OBG is an initialism for Ormeau Baths Gallery in Belfast, Northern Ireland.

OBG may also refer to:

• OBG/OBGYN, surgical–medical specialties dealing with the female reproductive organs
• OBG(W), Overwatch Battle Group (West), an Australian Army battlegroup
• OBG Ltd v Allan, a case on economic torts in English law
• Odesa Botanical Gardens, Ukraine
• Ofer Brothers Group, an Israeli family business
• Oprah's Big Give, a reality television series hosted by Nate Berkus
• Operation Board Games, a 2003 federal fraud investigation
• O.B.G., Overmassive black hole galaxy