ATG Entertainment, formerly The Ambassador Theatre Group (ATG), is a major international live entertainment organisation headquartered in the United Kingdom, with offices in Woking (head office), London, New York, San Francisco, San Antonio, Madrid, Mannheim and Cologne. ATG's key operations comprise three inter-related activities: venue ownership and management, ticketing and marketing operations, and show productions.

ATG runs more than 64 venues in Britain, the US and Germany. The