In short, the executive producer who serves as the head writer. The longer answer is that the showrunner is the person who gives the show its tone and direction.

The initial showrunner is usually the creator (frequently the writer of the {{pilot}}). As the years pass, the original showrunner may leave and a new one may join - this can often be a JumpTheShark or GrowingTheBeard moment.

Not to be confused with someone like a go-fer or someone who goes and get things for others - this person ''runs the show''.

!! Creator/Showrunners:
* Danny Arnold: ''BarneyMiller''
* DonaldPBellisario:
** ''MagnumPI'' (co-creator with Glen A. Larson, who had nothing to do with the show after the pilot)
** ''TalesOfTheGoldMonkey''
** ''Series/{{Airwolf}}''
** ''Series/QuantumLeap''
** ''Series/{{JAG}}''
** ''Series/{{NCIS}}'' (co-creator with Don [=McGill=])
* Rick Berman and Brannon Braga: ''Series/StarTrekEnterprise'' (Seasons 1-3)
* StevenBochco: ''HillStreetBlues'', ''LALaw'', ''NYPDBlue''
* StephenJCannell:''TheRockfordFiles'', ''Series/TheATeam'', ''TheGreatestAmericanHero'' (and most of his other series, in fact)
* David Chase: ''Series/TheSopranos''.
* Marc Cherry: ''DesperateHousewives''
* David X. Cohen: ''WesternAnimation/{{Futurama}}'', with co-creator MattGroening.
* David Crane and Marta Kauffman: ''{{Friends}}''
* Creator/LarryDavid and Jerry Seinfeld: ''{{Seinfeld}}'' (David left after season 7)
* TinaFey : ''Series/ThirtyRock''. Also plays a showrunner on the show.
* BryanFuller: ''PushingDaisies''
* Matt Groening, James L. Brooks & Sam Simon: ''WesternAnimation/TheSimpsons'' (season 1 and 2)
* Dan Harmon: ''Series/{{Community}}'' (seasons 1-3)
* Buck Henry: ''Series/GetSmart''. (co-creator Mel Brooks had little involvement with the series after the pilot)
* Mitchell Hurwitz: ''Series/ArrestedDevelopment''
* David E. Kelly: ''AllyMcBeal'', ''ThePractice'', ''BostonLegal''
* Creator/BryanKonietzko and Creator/MichaelDanteDiMartino: ''WesternAnimation/AvatarTheLastAirbender'' and its SequelSeries ''WesternAnimation/TheLegendOfKorra''.
* Eric Kripke: ''Series/{{Supernatural}}''
* Norman Lear: ''AllInTheFamily'', ''{{Maude}}'', ''SanfordAndSon''.
* Howard Leeds: ''SmallWonder''
* Ryan Murphy: Brad Falchuk and Ian Brennan [[FanNickname (collectively known as RIB)]]: ''{{Glee}}''
* Shonda Rhimes: ''GreysAnatomy'' and ''PrivatePractice''.
* GeneRoddenberry:
** ''The Lieutenant'' (1963-64)
** ''Series/StarTrekTheOriginalSeries'' (Seasons 1-2 only)
** ''Series/StarTrekTheNextGeneration'' (Season 1 only)
* Shawn Ryan: ''TheShield''
* Dan Schneider (y'know, Dennis from ''HeadOfTheClass''): ''Series/ICarly'', ''DrakeAndJosh'', and ''{{Victorious}}''
* Amy Sherman-Palladino: ''GilmoreGirls''(seasons 1-6)
* Paul Simms: ''NewsRadio''
* Creator/DavidSimon: ''TheWire'' and ''The Corner'' (He also wrote the book on which ''HomicideLifeOnTheStreet'' was based, and later joined the writing staff.)
* Creator/AaronSorkin: ''SportsNight'', ''TheWestWing'' (Seasons 1-4), ''Studio60OnTheSunsetStrip'', ''TheNewsroom''
* J. Michael Straczynski: ''Series/BabylonFive''
* Kurt Sutter: ''SonsOfAnarchy''
* Jeri Taylor: ''Series/StarTrekVoyager'' (jointly with co-creator Michael Piller for seasons 1-2; left after season 4)
* Heidi Thomas: ''Series/CallTheMidwife''
* Matthew Weiner: ''MadMen''
* DickWolf: ''Series/LawAndOrder''
* JossWhedon of MutantEnemy: "BuffyTheVampireSlayer" (except for season 6) and "Dollhouse"
* Bruno Heller: ''TheMentalist'', ''{{Rome}}''.
* Vince Gilligan: ''BreakingBad''.
* Jeff Marsh and Dan Povenmire: ''PhineasAndFerb''.

!! Showrunnners Who Took Over Existing Shows
* RussellTDavies: ''Series/DoctorWho'' - Series 1-4 + 2009 Specials.
* StevenMoffat: ''Series/DoctorWho'' - Series 5 onwards.
* Al Jean & Mike Reiss: ''TheSimpsons'' - Seasons 3 & 4
** David Mirkin: Seasons 5 & 6
** Bill Oakley & Josh Weinstein: Seasons 7 & 8.
** Mike Scully: Seasons 9 through 12.
** Al Jean: Season 13 to present.
* Journeyman producer Fred Freiberger became showrunner for the third season (often referred to as the [[SeasonalRot turd season]]) of ''Series/StarTrekTheOriginalSeries'', and became the [[MisBlamed scapegoat]] for all its problems.
* Ira Steven Behr took over ''Series/StarTrekDeepSpaceNine'' from Season 3 onwards, leading to much [[GrowingTheBeard facial hair growth]].
* Maurice Hurley became showrunner in the second seasons of ''Series/StarTrekTheNextGeneration'' and ''{{Baywatch}} Nights''. His work on the former helped the show move towards fully GrowingTheBeard, but his efforts on the latter proved that no matter how badly a show starts out, it can still JumpTheShark spectacularly.
* Michael Piller became the showrunner for the third season of ''Series/StarTrekTheNextGeneration'', and held the role for the rest of its run. He also acted as showrunner for the first two seasons of ''Series/StarTrekDeepSpaceNine'', and then joint showrunner (with Jeri Taylor) of the first two seasons of ''Series/StarTrekVoyager''.
* Brannon Braga became the showrunner of ''Series/StarTrekVoyager'' for seasons 5-6, departing in season 7 to develop ''Series/StarTrekEnterprise''. Like Freiberger before him, he became a major scapegoat, and is often blamed for ''all'' of the problems with the show's creative direction throughout its entire run.
* Kenneth Biller became the final showrunner for ''Series/StarTrekVoyager'' in season 7.
* Manny Coto took over primary showrunning duties from Rick Berman and Brannon Braga in the fourth season of ''Series/StarTrekEnterprise'', replacing Braga as executive producer. Although season 4 was generally considered the best one, it was too late to save the show from cancellation.
* Writer/Actor Paul Lieberstein, for seasons 5-7 of The Office.
* Writer/executive producer Sara Gamble is taking over as showrunner for ''Series/{{Supernatural}}'' as of Season 6.
* Neal Baer became showrunner of ''LawAndOrderSpecialVictimsUnit'' for season 2, replacing original showrunner Robert Palm, and has remained in that position for ''eleven seasons'', the longest tenure in franchise history. He will be moving on at the end of season 12.
* Rene Balcer assumed the role of showrunner for the original ''LawAndOrder'' twice: once in the late '90s, and again in the late noughties. In both cases, he left to helm a spinoff as the initial showrunner: First ''LawAndOrderCriminalIntent'', and then ''Law & Order: Los Angeles''.
* When Marti Noxon was promoted to executive producer for Season 6 of ''Series/BuffyTheVampireSlayer'', she also became showrunner for that season, since JossWhedon was initially preoccupied with the creation of a single episode ("Once More With Feeling"), as well as prepping ''{{Firefly}}''.
* After David Greenwalt left ''Series/{{Angel}}'', Jeffrey Bell took over as showrunner for the final two seasons. [[hottip:*:David Simkins, best known as a writer and producer on ''{{Charmed}}'', was brought in as showrunner for Season 4, but left due to creative differences after four episodes and was entirely uncredited; Bell replaced him and remained for the duration of the show.]] It is speculated that he will also act as showrunner on Joss Whedon's new ''Agents of S.H.I.E.L.D.'' show, since he's the only one of the other four listed executive producers to have showrunning experience.

!! Shows Where the First Showrunner Was Not the Creator
* ''Series/{{Lost}}'' is a hybrid as far as the creator/showrunner classification is concerned. Created/showrun by J.J. Abrams and Damon Lindelof (Jeffrey Lieber, who shares "created by" credit, had nothing to do with the show after writing the original pilot script) and run since early on by Lindelof and Carlton Cuse.
* ''Series/DoctorWho'', which has only had a 'showrunner' position since the 2005 revival. Created primarily by SydneyNewman, VerityLambert, Donald Wilson and C. E. Webber. The original series may be said to have divided the showrunner's duties between the producer and the script editor; sometimes the former (eg. Creator/JohnNathanTurner from 1980 to the cancellation) or the latter (eg. Douglas Adams, 1979; Andrew Cartmel, 1987-89) seemed to have more of the role.
** Likewise, ''Series/{{Torchwood}}'' and ''Series/TheSarahJaneAdventures'' were both technically created by RussellTDavies, but the initial showrunners were Chris Chibnall and Phil Ford respectively. Davies later took full control of ''Torchwood'' starting with its third series, while Ford remained showrunner on ''The Sarah Jane Adventures'' for its entire run.
** BigFinishDoctorWho, the audio series, has Creator/NicholasBriggs (the voice of the Daleks) as its ShowRunner.
* An odd example in ''WizardsOfWaverlyPlace'': The show's creator, Todd J. Greenwald, remains on-staff as a writer and producer, but he is ''not'' the showrunner - that honour went to Peter Murrieta for the first three seasons. (In the fourth season, he left and Greenwald stayed on - but Greenwald still did not become the showrunner.)
* Edward Allen Bernero wasn't the creator of Series/CriminalMinds, but was its showrunner from the pilot to the end of the sixth season.
* If a film series can count, producer David Heyman is essentially the showrunner of the ''Film/HarryPotter'' movie franchise. Directors come and go and Heyman is often the one who selects them.
* "Showrunning" duties on ''WesternAnimation/StarTrekTheAnimatedSeries'' were divided between story editor D.C. Fontana and animation director Hal Sutherland; Gene Roddenberry, despite receiving creator credit, had no involvement with the series (though he was listed as the "Executive Consultant", in a harbinger of [[Film/StarTrekIITheWrathOfKhan things to come]]).
* David Greenwalt ran Joss Whedon's ''{{Angel}}'' for the first three seasons, before leaving to work on ''Miracles''.
* Tim Minear ran Joss Whedon's ''{{Firefly}}''.

!! Showrunners in Fiction
* ''Series/ThirtyRock'': Liz Lemon
* ''Studio60OnTheSunsetStrip'': Matt Albie and Danny Tripp
* ''Almost Perfect'': Kim Cooper
* ''The TV Set'': David Duchovny plays beleaguered showrunner Mike Klein.

!! Long-Running Shows That Never Changed Showrunners
* ''CurbYourEnthusiasm'': Seven seasons, showrunner Creator/LarryDavid. The main character? [[AsHimself Larry David, a showrunner]].
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