Olympic Games

Original Gangster, see Gangster

OG: Optimized Gaia, theory the earth optimizes itself to promote life, and popular movement to Promote Human Progress in Harmony with the Natural World.

Own goal, in association football, a goal scored by a player in their own side's goal

Obstetrics and gynaecology

OG: Original Gangster, an album by Ice-T

Olive Garden Casual Italian Restaurant

Old Gold, a dark yellow

Offensive Guard, see Guard (American football)

Original Gravity, see Gravity (beer)

Objective Glass, see Objective (optics)

Old Giggleswickian, a former pupil of Giggleswick School

Old Gower, a former pupil of University College School

Old Gregorian, a former pupil of Downside School

Old Greshamian, a former pupil of Gresham's School

Outpost Gallifrey, a Doctor Who fansite.

OG, a Singapore-based department store.

the IATA airline code for One-Two-GO Airlines.

Opera Ghost. The alternate name of The Phantom of the Opera in Andrew Lloyd-Webber's musical.