The Airbus A380 is powered by four Rolls-Royce Trent 900 engines in its standard passenger version.
The A380 is Airbus’s large double-deck wide-body airliner. Its four-engine design was developed for very high passenger capacity and long-range operations, and airlines could select among several engine suppliers. The Rolls-Royce Trent 900 was one of the engine options and powered many passenger A380s.
The A380 is not defined by one engine model alone. Other aircraft used Engine Alliance GP7000 engines, so saying that every A380 used Trent 900 engines would be incorrect. The question specifies the Rolls-Royce-powered configuration.
The A340 is another Airbus family with four engines, which causes frequent confusion. However, the A340 is a conventional single-deck wide-body family, while the A380 has two full passenger decks along much of its fuselage. The A350 and A330 are twin-engine aircraft.