- Occi-Expert
- Ocean Crush Harvest: Match 3 Puzzle Free Games
- Octopus Hunter
- Odd and Even numbers
- Odd Emoji Out game
- Odd One Out - Trivia Quiz Game
- Odd one out game
- Odd Out - The Brain Game
- Oden Cart 2 A Taste of Time
- Office Trivia Quiz
- Offroad Police Car Driving
- Oida Quiz - Das österreichische Mundart und Dialekt Quiz
- OiKID PK王
- Oil Painting Color by Number
- OK: Drag and drop mappen balls
- Okay?
- Old Brick Machine Game
- Old clock and sweets' parlor
- Olodo
- OMBible
- Omnigrams
- Omra Quiz Live
- On Your Head
- ONCE fandom TWICE
- ONCE fandom TWICE
- OnClick!
- OncoSwiper
- One Brain – Elevate Your Mind
- One By One - Math Game
- Amy And Her Friend
- One Hit Cowboy
- One Line Number - Chain Puzzle
- One Line: One Touch Drawing
- One second before...?
- One Sudoku
- One Tap Calculator 2
- One Thousand Pinball Dots
- Onet Connect Animal - 1010, Quadris Mania
- Onet Connect Animals Deluxe
- Onet Connect PVP Version
- Onet Fruit Classic
- Onet - Mahjong Connect
- Onet Online
- Onletters
- Online Hangman Word Game
- Online Snakes
- Only 3 Words
- Only Fools And Horses Quiz
- Open Door - Escape Games
- Open One Photo Plus
- Operation Calculus
- Opi viittomaan
- Ordena la línea del tiempo
- Ordne Die Bunten Bälle
- Ordne Die Bunten Bälle LT
- Orijinz
- Osaka Map Puzzle
- Oscar Winners Trivia
- Osmanlı Bilgi Yarışması Oyunu
- Osmanlı Tarihi Bilgi Yarışması
- OT Country Quiz
- OtaQuiz
- OuPaSav
- Our Presidents
- Out of the Loop
- Outsmarted - Companion App
- Ov e, Inch e - gushakir nkary
- Overlap: Spatial Reasoning
- OWARDS Trivia
- Owl Teach You Time