The number of page types in each namespace:
| ObfuscatingStupidity | subpage | 11 |
| redirect | 1 | |
| ObliviousGuiltSlinging | subpage | 3 |
| ObliviousToHisOwnDescription | subpage | 5 |
| ObliviousToLove | subpage | 11 |
| redirect | 1 | |
| ObnoxiousInLaws | subpage | 9 |
| ObviousBeta | subpage | 1 |
| ObviousJudas | subpage | 1 |
| ObviouslyEvil | subpage | 8 |
| ObviousRulePatch | subpage | 12 |
| OCStandIn | subpage | 3 |
| OcularGushers | subpage | 2 |
| OddballInTheSeries | subpage | 1 |
| OddFriendship | subpage | 8 |
| OddlyNamedSequel2ElectricBoogaloo | subpage | 1 |
| OddNameOut | subpage | 6 |
| OfficerAndAGentleman | subpage | 2 |
| OfficialCouple | subpage | 8 |
| OffingTheOffspring | subpage | 5 |
| OffOnATechnicality | subpage | 5 |
| OffscreenMomentOfAwesome | subpage | 11 |
| redirect | 1 | |
| OffscreenTeleportation | subpage | 4 |
| redirect | 1 | |
| OffWithHisHead | subpage | 1 |
| OhCrap | subpage | 27 |
| redirect | 5 | |
| OhMyGods | subpage | 1 |
| OlderThanTheyLook | subpage | 10 |
| redirect | 1 | |
| OlderThanTheyThink | subpage | 19 |
| redirect | 3 | |
| OldMaster | subpage | 5 |
| OldSoldier | subpage | 4 |
| OminousLatinChanting | subpage | 5 |
| redirect | 1 | |
| OminousPipeOrgan | subpage | 1 |
| OmnicidalManiac | subpage | 6 |
| OmnidisciplinaryScientist | subpage | 3 |
| OnceMoreWithClarity | subpage | 1 |
| OnceOriginalNowCommon | subpage | 14 |
| redirect | 2 | |
| OncePerEpisode | subpage | 2 |
| OnceUponATime | examples | 7 |
| OneBookAuthor | subpage | 3 |
| OneDegreeOfSeparation | subpage | 4 |
| OneHitKill | subpage | 3 |
| OneHitWonder | subpage | 7 |
| redirect | 1 | |
| OneHourWorkWeek | subpage | 1 |
| OneManArmy | subpage | 13 |
| redirect | 2 | |
| OneMarioLimit | subpage | 1 |
| OneOfTheBoys | subpage | 5 |
| OneOfUs | subpage | 9 |
| OnePiece | examples | 8 |
| OnePieceWholeCakeIslandArc | examples | 7 |
| OneSceneWonder | subpage | 16 |
| redirect | 1 | |
| OneSteveLimit | subpage | 20 |
| OneThousandWaysToDie | subpage | 4 |
| OneTrueThreesome | subpage | 8 |
| OneWingedAngel | subpage | 10 |
| OneWordTitle | subpage | 10 |
| redirect | 1 | |
| OnlyAFleshWound | subpage | 7 |
| OnlyBadGuysCallTheirLawyers | subpage | 2 |
| OnlyKnownByTheirNickname | subpage | 12 |
| redirect | 1 | |
| OnlyOneName | subpage | 1 |
| OnlySaneMan | subpage | 14 |
| redirect | 2 | |
| OnlySixFaces | subpage | 4 |
| OnlyTheCreatorDoesItRight | subpage | 2 |
| OnSetInjury | subpage | 1 |
| OOCIsSeriousBusiness | subpage | 18 |
| redirect | 3 | |
| OohMeAccentsSlipping | subpage | 3 |
| redirect | 1 | |
| OpeningNarration | subpage | 6 |
| OpenSecret | subpage | 7 |
| OppressiveStatesOfAmerica | subpage | 1 |
| OrphanedSeries | subpage | 2 |
| OrphansPlotTrinket | subpage | 2 |
| OtherMeAnnoysMe | subpage | 6 |
| OTT | subpage | 3 |
| OurAngelsAreDifferent | subpage | 6 |
| OurDemonsAreDifferent | subpage | 6 |
| OurDragonsAreDifferent | subpage | 12 |
| redirect | 3 | |
| OurElvesAreDifferent | subpage | 2 |
| OurGhostsAreDifferent | subpage | 2 |
| OurGodsAreDifferent | subpage | 1 |
| redirect | 1 | |
| OurMermaidsAreDifferent | subpage | 2 |
| OurMissBrooks | subpage | 2 |
| OurVampiresAreDifferent | subpage | 14 |
| redirect | 1 | |
| OurWerebeastsAreDifferent | subpage | 9 |
| OurWerewolvesAreDifferent | subpage | 9 |
| OutdatedByCanon | subpage | 2 |
| OutGambitted | subpage | 9 |
| OutlivedItsCreator | subpage | 1 |
| OutlivingOnesOffspring | subpage | 4 |
| redirect | 2 | |
| OutOfCharacterAlert | subpage | 3 |
| OutOfFocus | subpage | 2 |
| OutOfGenreExperience | subpage | 1 |
| OutOfOrder | subpage | 2 |
| OutsideContextProblem | subpage | 4 |
| Overheating | subpage | 2 |
| OverlyLongGag | subpage | 15 |
| OverlyLongName | subpage | 13 |
| redirect | 3 | |
| OverlyLongTongue | subpage | 1 |
| OvershadowedByAwesome | subpage | 13 |
| redirect | 2 | |
| OvershadowedByControversy | subpage | 18 |
| OverusedRunningGag | subpage | 1 |
| Overwatch | subpage | 3 |
