- Online Mahjong Solitaire
- Only 1 color per line
- Only Fools And Horses Quiz
- Only for Geniuses
- Only Pop The Blue Bubbles
- Onnect Flowers Match Puzzle
- Onnect Tile Match: Onet Puzzle
- Onnect Onet: Tile Star
- ONO: Think Straight
- Cause Effect
- Opart
- Opdoku = Calcudoku + Mathdoku
- Open 100 Doors - Christmas!
- Open 99 Doors
- All Lit
- Open Bigger Surprise Capsule
- Open Door - Escape Games
- Open Giant Surprise Puppycage!
- Open House Hidden Object Games
- Open House: Meet Friends
- Open It!30 Doors
- Open One Photo
- Open One Photo Plus
- Open Puzzle Box
- Open Road For King Puzzle
- Open The Classic Door
- Open The Classic Door
- Open The Classic Door Season 3
- Opening day of a fresh baker’s
- Open the door - fun games
- Operation Optics
- Operation Santa
- Operation: Survive Runner 3D
- Operator service
- Operators - Math Exercises
- Opinion Game
- Opposites - HD
- Opposites 1
- Opposites 2 - Matching game
- Opposites learn and play
- Oran's Table
- Orange
- Orange Ball and Black Holes
- Orange HD
- Orange to Juice Puzzle
- Orb Lines, Neo Lines 98
- Orba
- Orbi.go - reach the center
- Orbit - Defy gravity
- Orbit - Playing with Gravity
- Orbit 2D
- Orbit Bender
- Orbit HD
- Orbit Path - Space Physics Game
- Orbital
- Orbiter Ext
- OrbitR
- Orbolo
- Orbox B: Rebirth
- Orbs Match Christmas
- Orbs Match Christmas Puzzle
- Orbs Match - Swipe sort & pop
- Orbs of Eternity
- Bubble Pop: Balloon Shooter 3D
- Orbu: AR Puzzler
- Orca Puzzles for Kids Free Jigsaw Wonder Edition
- ORCade board brain block match
- Orcrest
- OrcrestLite
- Ordena la línea del tiempo
- Order 9
- Order In The Court!
- Ordered Knight
- OrderFromChaos vla
- Ordinary Puzzles
- Ordkjeder