->''"The edges of the Shikra blade have been honed to the thickness of a single atom. I must keep my hand ''very still'', for fear that one slip will cut you... in half."''
-->-- '''Qetesh''', ''Film/StargateContinuum''

Weapons that have been sharpened to a single atom are a particular type of AbsurdlySharpBlade that are ''so'' sharp, their cutting edge can be measured in terms of atoms or molecules, often being just a single molecule wide. This usually gives the weapons AbsurdCuttingPower, but generally requires the blade to be made out of some sort of {{Unobtanium}} to maintain that sharpness without dulling instantly (or just shattering into a million pieces) the first time it's used. For these reasons, the trope is most frequently encountered in ScienceFiction settings.

A common term used for this is "monomolecular". Most often seen with [[ILikeSwords knives or swords]], but occurs from time to time with RazorWire, too. This can be particularly troublesome, as monomolecular wire is usually functionally invisible, and walking into one can slice through vital bits [[YouAreAlreadyDead without being immediately noticed]].

A weapon is only an example of this trope when a ''specific'' (very small) width is given for the blade's edge; if no specific measurement is given, then it's just an AbsurdlySharpBlade.



[[folder:Anime and Manga]]
* Eve from ''Manga/BlackCat'' managed to manipulate her PrehensileHair to do this later in the manga.
* In ''Anime/KiddyGrade'', Sinistra and Dextera's ship can split into two, creating a 'monodimensional' blade between the halves.
* Mamoru's katana from ''Manga/UntilDeathDoUsPart'' is a high tech monomolecular blade, able to break the bonds between molecules and cut anything (if the katana's angled properly). At one point he cuts a gun in half; when the pieces are pushed back together, it appears as if the gun was undamaged, because the cut is that sharp.
* Quinn Garland of ''Manga/MagicalRecordLyricalNanohaForce'' slashes at Tohma, Erio, and Caro with an unknown attack from her sword at long-range that isn't magic or some sort of Divider or Virus based power that could slice through things that normal swords can't slice. It's eventually revealed to be her extending her sword by projecting a particle-like blade from its tip.
* A non SciFi example shows up in ''Anime/SaintSeiyaOmega''. Hyperion's sword, the Cataclysm Slash, can cut a proton in two. In this case, the sword was forged and given to him by a god.
* In ''Anime/HellsingUltimate'', Walter C. Dornez, the Hellsing family's personal butler, uses a set of monomolecular razor wires to devestating effect in combat, where they are shown capable of effortlessly dismembering and slicing apart armies of humans and ghouls alike. It can cut through steel and concrete, and at one point they are even used to bring down several Black Hawk helicopters. Walter controls them as extensions of his own body, and they seem to be of infinite length and durability, as they never break in the series.

* Nemesis, a member (and former enemy) of ''ComicBook/AlphaFlight'', uses a saber whose blade is only a single molecule wide.
* In ''ComicBook/KingdomCome'' Franchise/WonderWoman has a magic sword that is sharp enough to "carve the electrons off an atom". Leaving aside the ways that doesn't actually make sense, it suggests a blade with an edge thinner than an atom. Franchise/{{Superman}} accidentally cuts himself on the blade.

* The assassin in ''Film/JohnnyMnemonic'' has a monomolecular wire concealed in a prosthetic thumb tip. The movie makes it glow because an invisible wire whip wouldn't be interesting to look at.
* ''Film/TheManInTheWhiteSuit'' is a film about the invention of a completely dirt-proof fabric. It's not emphasised, but it's mentioned in passing in the dialogue about the development of the new material that the threads are, in effect, molecular monofilaments causing problems in handling and cutting them. It evidently doesn't occur to any of the characters that this could have other applications. This may be one of the earliest occurrences of the concept in fiction.
* In ''Film/StargateContinuum'', the blade held by Ba'al (later stolen by Qetesh) has an edge "only one atom thick", making it thin enough to cut Lord Ba'al clean in half.

* The variable sword used in the ''Literature/KnownSpace'' stories of Creator/LarryNiven is a length of monomolecular wire held straight by a projected stasis field. There's a little red ball at the end of the wire so the wielder can tell where the otherwise invisible "blade" ends.
** ''The Descent of Anansi'', also by Creator/LarryNiven features another monofilament cable where, in effect, a space shuttle is lowered to Earth on a cable. At one point one of the baddies drifts into the cable and realises that it is already inside the faceplate of his spacesuit by the time he notices anything.
* The Posleen in John Ringo's ''Literature/LegacyOfTheAldenata'' have monomolecular blades that can carve up an Armored Combat Suit as easy as a Ginzu knife cuts through a tin can. And then they can slice a tomato so thin you can read a newspaper through it!
* ''Brasyl'', by Creator/IanMcDonald, one-ups monomolecular-edged knives with the Q-blades: they have an edge that can cut quantum strings. Y'know, the stuff that decides matter ''is'' matter; essentially erasing anything the edge comes into contact with, with zero resistance. If a Q-blade ever [[LikeCannotCutLike breaks]], the flying shrapnel will slice through soil and rock, ultimately sinking towards the Earth's core.
* In ''Literature/SnowCrash'', by Neal Stephenson, Dmitri "Raven" Ravinoff uses knives made of knapped glass with monomolecular edges. They slash through Kevlar body armor, thick bamboo and people quite effortlessly, though they're [[spoiler:still prone to shattering, which is unfortunate as his final opponent just happens to be carrying a sonic weapon]].
* The main character, as well as just about everyone, in Sergey Lukyanenko's ''Literature/ALordFromPlanetEarth'' series wields a monoatomic sword called a planar sword. The main character, in fact, [[DualWielding dual-wields]] them and carries them on his back. As expected, the swords can cut through any known material. In one-on-one combat with planar swords, one of the swords will invariably slice through the other. The trick is making sure you hit the opponent's sword at just the right angle with a thinner blade. The blade dulls with each strike and swing, requiring it to be periodically sharpened by a button on the hilt (a blade can only handle about 1500 sharpenings). Being a battle-hardened Earthling, the main character comes up with some nonstandard (and questionable) applications for the technology. He creates a throwing disc with monoatomic edges, which can literally take a person's head off. Later, he uses smaller hollow-point monoatomic discs that fire from a blowgun.
* Flann O'Brien's ''Literature/TheThirdPoliceman'' features a spear so sharp that if you were to prick yourself with it, your finger would begin to bleed about 2 inches before the point appeared to reach your finger. In fact, when your finger starts to bleed, the spear point had penetrated your skin 2 inches ago, but was so thin it slipped between the atoms of your finger without causing any damage.
* In ''Man of the Ice Garden'', Vuko Drakkainen, a visitor from future Earth to a primitive planet, uses a Nordland Aeronautics shinobi ken sword with monomolecular blade. He once made a swing at a "monster" and accidentally cut through the ceiling without even noticing until some of its parts fell down. He also accidently cut through the dog, which hit the ground [[HalfTheManHeUsedToBe twice]].
* In the Franchise/StarTrekNovelVerse, the Tholians have blades with monomolecular edges. The swords become important to the plot in the novels [[Literature/StarTrekTheLostEra ''The Sundered'']] and [[Literature/StarTrekVanguard ''Reap the Whirlwind'']].
* In the ''Literature/FirebirdTrilogy'', the edges of crystaces' blades are precisely one atom thick.
* ''Literature/TheDarkSideOfTheSun'' by Terry Pratchett features a monomolecular blade (which shatters when swung against a villain gifted with luck manipulation).
** They came up again in his ''Literature/{{Discworld}}'' series - both Death's scythe and sword have edges one molecule thick. Thinner, in fact - they glow blue because of the energy released when they cut the air apart.
* ''Franchise/StarWars'' [[Franchise/StarWarsExpandedUniverse Expanded Universe:]]
** In the short story "[[HoYay/StarWarsExpandedUniverse Side Trip]]", Jodo Kast, who is actually Thrawn in disguise, gives one to [[spoiler:Corran Horn]].
** Blades like this make an appearance in the novel ''Specter of the Past'' by TimothyZahn, in the form of the Xana "molecular stiletto." Depicted somewhat realistically, in that it's described as being capable of cutting through almost anything, but is extremely delicate, with even the carefully executed cutting of a hard surface (such as a lock) being as likely as not to ruin the blade.
* In the ''Literature/{{Sten}}'' novels, Sten has a small knife in his forearm (within a surgical compartment) that can cut through virtually anything. It's five molecules wide at its tip.
* Matthew Mantrell wields one in at least the first book of ''Literature/AWizardInRhyme''. It's also made of a single black diamond. [[AWizardDidIt And magic.]]
* In ''[[Literature/TheShipWho The City Who Fought]]'' by Creator/AnneMcCaffrey and Creator/SMStirling, Joat lays a trap using monomolecular wire. The effects are messy.
* In ''Literature/LeftBehind'', Chaim Rozenweig creates a blade like this, so sharp that a falling date splits in two by grazing the blade. He then buries the blade in the head of the leader of the world.
* ''The Fountains Of Paradise'' by ArthurCClarke has something very similar to this, but, [[MohsScaleOfScienceFictionHardness Clarke being Clarke, it is depicted in a manner closer to scientific reality]] than most examples on this page. Construction of a SpaceElevator becomes a realistic possibility after the development of a process to manufacture a "pseudo-one-dimensional diamond crystal" a few microns thick in continuous lengths, forming invisible fibres of enormous tensile strength. Its main application is as a tension member (of course), not as a weapon, though much attention is given to the handling difficulties and dangers of such a material. Its sharpness is also reasonably realistic--it is extremely sharp, but not [[AbsurdlySharpBlade absurdly so]]--it can easily cause severe wounds through mere inattention to handling, but to deliberately cut down a tree with it takes a couple of minutes, and the length of time it takes to cut through a metal fastening with it is an important element at one point in the story.
* From the second book onwards in the ''Literature/HIVESeries'' series by Mark Walden, Raven fights with a pair of katanas with a variable geometry monomolecular force-field.
* The ''Literature/{{Deathstalker}}'' handwaves the existence of such blades by explaining that the edge is actually created and maintained by a special force field. Since they can be deactivated, it makes the blades much safer to handle, store, and hide as an assassin's tool.
* In Creator/DanielKeysMoran's ''The Long Run'', there is the "emblade" (hand-held knife) which goes along with "fineline" (a spool of wire of any length). Both appear to have an edge approximately one molecule wide, allowing them to easily cut through anything. The emblade is useful for cutting holes in walls and floors, because you can simply glue the piece back into place and it is hard to detect. Fineline is useful for putting in front of missile ports, with unfortunate consequences for the missile when it is fired.
* Brazilian novel ''Espada da Galáxia'' does it with an extra twist. Not just is the blade that names the book sharpened to a single atom, it's also made of "metallic Hydrogen", making its edge as thin as the smallest atom.
* In the ''Literature/HisDarkMaterials'' trilogy the Subtle Knife has one edge sharpened so finely that it can cut through any material, the other edge is sharp enough to cut a hole in the universe leading to another one.

[[folder:Live Action TV]]
* ''Series/{{Andromeda}}'' once depicted a "monomolecular lash", basically a ''whip'' that can cut through anything and has to emit a glow in order for anyone to see it. Since it cuts through its wielder as easily as anything else, it's exceedingly difficult to master without killing yourself with it and expert users of it are very rare, mostly making it AwesomeButImpractical.

[[folder:Tabletop Games]]
* ''TabletopGame/{{Warhammer 40000}}''
** Most combat blades have an edge one molecule thick. This includes combat knives, swords, some types of ammunition, etc. Such blades are quite commonplace in their armies. They're no more effective at punching through armour for it, however, unless you're playing ''TabletopGame/DarkHeresy''. In it (and other Fantasy Flight Games' 40k [=RPGs=]), melee weapons can be upgraded to have monomolecular edges, increasing their armour penetration. In most of the games this can only be done on bladed and [[ChainsawGood chain]] weapons, but early editions of ''Dark Heresy'' didn't have this limitation, allowing you to create monomolecular hammers and staves. However, the rules stated that an alternative explanation had to be given for the increased penetrative power; there were no monomolecular hammers or staves, they just functioned the same with a different name given to the technology behind it.
** The [[OurElvesAreDifferent Eldar]] use a variety of monomolecular weapons:
*** The most common are "shuriken" weapons. The weapon's magazine is actually a large mostly-cylindrical chuck of matter, and the upper receiver shaves off monomolecular discs. Thousands of them. [[FlechetteStorm Per second]].
*** Harlequin units have a weapon called The Harlequin's Kiss, which is a hundred metre long monomolecular wire, delivered in a neat bundled package with a punch, at which point it unfurls, liquifies the target's internal organs, and then snaps back into the delivery device.
*** Heavier Eldar "spinner" weaponry makes use of "webs" of monofilament cord. They have artillery that sends clouds of this stuff slowly drifting down over the battlefield, invisible until the moment your entire squad falls apart into little chunks.
* ''TabletopGame/FadingSuns'' has wireblades -- monomolecular swords that will cut through anything with ease. In game mechanics, this means they ignore any armor the opponent is wearing.
* ''TabletopGame/{{Shadowrun}}''
** The game has monomolecular axes that possess a monofilament edge capable of cutting through virtually anything. It tends to lose its edge quickly though. In later editions, other bladed weapons could be outfitted with a monofilament edge. There's also a monofilament whip, noted by 'in character' reviews to be as big a threat to the user as to a potential enemy.
** At least one supplement had 'consumer annotations' that lampshaded the difference between mere monofilament and a monomolecular filament.
---> "Don't believe the hype, kiddies! That's not a ''real'' monomolecular filament. After all, my bootlace is monofilament too, and I'm not going to be lopping any limbs off with that."
* ''TabletopGame/{{GURPS}} Ultratech'' has a number of (increasingly super-science) ways of working this into the game mechanics. Superfine blades divide damage resistance by two. Monowire blades divide damage resistance by ten. Nanothorn blades divide damage resistance by ten and ''shreds'' the bonds that hold the atoms in molecules together.
* ''TabletopGame/EclipsePhase''
** Monofilament Swords are a common bladed weapon made with self-sharpening smart materials. They easily have some of the highest penetration and damage of any melee weapon in the game. [[NeverBringAKnifeToAGunFight They're still no match for all but the lightest of firearms]] when it comes to stopping power, though.
** The 'exotic' [[RazorFloss Monowire Garrote]] has the most armour penetration of any melee weapon and inflicts decent damage, although the description notes the wire has fairly low tensile strength and can often break easily.
* ''{{TabletopGame/Infinity}}'' has monofilament as an ammunition type that is issued almost exclusively to the elite troops of every army. They're not exactly common, but have a nasty effect: anything they hit, if it fails an armor roll, is [[OneHitKill instantly destroyed and removed from the table]], regardless of it's remaining [[HitPoints wounds or structure]]. This includes [[MiniMecha TAGs]], named characters, any {{One Man Army}} that might be around. It's {{hand wave}}d in the background as being stabilized through an EM field.
* ''TabletopGame/DarkConspiracy'' supplement ''[=DarkTek=]'': The Monofilament Machete's blade is 3-4 molecules wide and 1 meter long, with a small red ball on the end so the user can gauge their swing. It can cut through almost any solid substance, including armor.
* R. Talsorian Games' ''TabletopGame/{{Cyberpunk}} 2020'' had the Monoknife and MonoKatana, both extremely sharp.
* ''TabletopGame/{{Traveller}}'', ''Megatraveller Journal'' #3, "Worldguide: Vincennes": The Tech Level 16 world Vincennes creates swords of extruded monofilament construction which have astounding penetration.
* Judges Guild magazine ''The Dungeoneer Journal'' #23, article "Magic Item Generator". One of the possible magic items is a Monomolecular Wire that's a single molecule thick. It can cut through any substance but must be [[RazorFloss anchored at each end to be used as a weapon (e.g. as a garotte)]].

[[folder:Video Games]]
* A manual for ''Franchise/StarCraft'' states that Ultralisk blades are monomolecular. This seems to be a case of a writer simply getting carried away with RuleOfCool, as there is no indication elsewhere that this is actually the case. For one the blades are absolutely massive, and look more designed for smashing than slicing, and having monomolecular blades implies a degree of finesse the ultralisk certainly lacks. Apparently other writers agree, as depictions of ultralisks mostly show them smashing enemies aside with their blades, rather than slicing right through them as would be the case if their blades really were that sharp.
* In the ''ComicStrip/BuckRogers'' games, mono(molecular) knives and swords are described in this way. In true RPG fashion, they are superior to most of the 25th-century guns available.
* In ''VideoGame/OneMustFall2097,'' the manual describes Thorn's spikes and Katana's blades as using "monofilament technology".
* Cerberus Phantoms (ninja mooks) in ''VideoGame/MassEffect3'' carry monomolecular swords, and the player-useable "omni-blades" are equally sharp. These blades increase their practically in two ways: one, the blades are "flash-forged" by high-precision portable fabricators, so they can be renewed as needed; two, they're supported by Mass Effect fields which can also make them {{Hot Blade}}s.
* The Dragon Tooth Blade from ''Videogame/DeusEx'' is said to be made of self-organizing nanites which keep the blade always molecularily sharp.
* The Avalon [=WarMech=] in ''VideoGame/{{Implosion}}'' wields a sword with a mono molecular edge.
* The retractable blades on the Scorpions in ''VideoGame/UnrealTournament2004'' are mentioned to have an edge that is exactly one atom thick. However, while they will instantly cut any on-foot opponent they touch in half, they break off if they touch anything else.
* ''Videogame/DungeonsOfDredmor'': The Monofilament Sword is a more typical application of this trope, being a single atom (or thaumaturgon as the game calls 'em) thick, and doing ''vicious'' damage. A slightly stranger application is the Moravician Bushdagger, made by the titular (drunk) wizard Moravic on a bet at a pub. The blade starts out normal, then starts branching and branching near-infinitely until every single tip is a single thaumaturgon thick. It stabs a million wounds in one thrust, and is probably the best dagger in the game thanks to it (despite looking like a metallic bush). Unfortunately it also got Moravic banned from the aforementioned pub.
* Of the two times a ''Franchise/FinalFantasy'' localisation has [[TooLongDidntDub ever bothered translating]] the "Zantetsuken" move, one of them, ''VideoGame/FinalFantasyVI'', calls to mind this trope: "Atom Edge".

[[folder:Web Original]]
* Atomic and Subatomic blades in ''Literature/{{Phaeton}}''
* Alton Brown once wrote a short story on his blog about a kitchen apprentice who sharpened a chef's knife until it became one of these...and accidentally set off a nuclear blast while chopping a tomato.
* The long-defunct parody shopping website [[https://web.archive.org/web/20030122084059/http://villainsupply.com/ Villain Supply]] offered this type of wire for sale as a henchman tool.
* ''Wiki/SCPFoundation''
** [[http://scp-wiki.net/scp-314 SCP-314 ("Motion-Seeking Blade")]] The blade is described as "sharpened to a molecular level".
** [[http://scp-wiki.net/scp-608 SCP-608 ("Fractal Tinsel").]] SCP-608 is a fractal with infinitely and progressively smaller branches radiating from it. Branches of monofilament size and smaller can slice through other substances at a molecular or even atomic level.
** [[http://www.scp-wiki.net/scp-1320 SCP-1320 ("Refractive Explorers").]] SCP-1320 have extremities that are sharpened to a thickness of a few dozen nanometers. They can use them to cut through solid objects at a molecular level.
** [[http://www.scp-wiki.net/scp-585 SCP-585 ("Sharpeners")]] can do this to pencils. After 100 rotations, the point is so thin it ''splits atoms''.
** [[http://www.scp-wiki.net/scp-2502 SCP-2502 ("Be Sharp")]]. SCP-2502 is a compact disc whose edge has zero thickness. When its edge encounters matter it cuts through it like a hot knife through butter. After passing through matter for a while it will eventually slow to a stop due to friction.

[[folder:Western Animation]]
* In ''WesternAnimation/BatmanBeyond'', Assassin Curare uses a monomolecular sword that effortlessly cuts through anything standing in the way of her swings. During the analysis, Bruce mentions the sword is sharpened by lasers to have an edge as wide as a single molecule.

[[folder:Real Life]]
* Contemporary nanotechnology is actually capable of creating blades like this, but, with a few exceptions (see below, mostly), not ''sustaining'' them. Regular blades go dull; an edge that can be measured in atoms becomes an ordinary knife very quickly if those atoms do not have ''very'' strong atomic and intermolecular bonds.
* Knapped obsidian blades are a small and measurable number of molecules in thickness. And while diamond is the harder material, obsidian can be made ''sharper''. The greatest of care should be used in handling obsidian knives and arrow points etc because they can remain truly Absurdly Sharp even centuries after being made and will cut you badly with even the slightest touch. The drawback of course is that being basically an exotic form of glass, they wear out quickly in use.
** Obsidian blades are still used in eye surgery when a clean cut is needed.
** Anthropologists and paleontologists have "tested" the technology available to Stone Age humans by using hand-knapped obsidian blades to butcher an elephant's carcass.
** Obsidian can be made up to 100 times sharper than steel (the cutting edge can be reduced to 3 nanometers thick). According to TheOtherWiki, "even the sharpest metal knife has a jagged, irregular blade when viewed under a strong enough microscope; when examined even under an electron microscope an obsidian blade is still smooth and even." For surgical application, the blades are so sharp that in certain circumstances, no anesthetic is necessary to make the cut. [[http://4.bp.blogspot.com/-sswf3heCoxg/T_nNlzq2F0I/AAAAAAAARNU/F05SmCWV34A/s1600/obsidian+razor.png (See here)]]
** Many Aztec weapons had obsidian blades or points. The macuahuitl is a wooden sword with the blade made out of obsidian shards. According to Spanish accounts, a single blow from a macuahuitl can decapitate a horse. When they tested it out on DeadliestWarrior, it decapitated the model-horse in three hits and [[LudicrousGibs left a pretty big mess.]]
* Single-layer graphene is probably the sharpest blade that can be made with conventional matter. It's a single atom thick, and since the atom is carbon (atomic number 6, ''very'' low on the periodic table), it's thinner than you can get pretty much any substance without distributed electron orbitals to stiffen it, and it's essentially the strongest material known that operates on that scale. Per unit area, it's stronger than diamond, though diamond is superior at greater thicknesses, due to graphene's weak inter-layer binding.
** Carbon nanotubes are basically graphene sheets rolled up into a tube, so by definition are a single molecule thick.
** Graphene monolayer is found to be toxic because the jagged edges they form can pierce cell membrane [[https://archive.is/LOsqS easily]].
* To prepare a slide for an electron microscope, a diamond or broken glass blade is used to get a less-than-paper-thin slice. Once properly sharpened, it's about a hundred atoms wide, and it will slide through your hand as easily as through the air. Glass blades are sharper (and cheaper) but wear out after a few dozen slides; diamond blades last almost forever.
** And if it slices through your hand, not only are you bleeding horribly, but you'll need a new diamond blade, [[AddingInsultToInjury because cutting through your flesh just broke the damn thing.]]
* Best-quality tips of scanning probe microscopes are ''literally'' single atom-wide and able to resolve individual atoms of the sample.