The UCI Mountain Bike & Trials World Championships are the world championship events for mountain bike racing events in cross country, downhill, four-cross and trials riding events. It is organized by the Union Cycliste Internationale (UCI), and winners are presented with a gold medal and are entitled to wear the rainbow jersey for a full year in future events of the same discipline. Unlike other UCI-sanctioned races, the World Championships is organized by nationality, not by commercial teams. The race is usually held towards the end of the season.
The first world championships took place in Durango (USA) in 1990, consisting just of cross country and downhill events. Trials riding was added in 1992. The dual slalom event was added in 2000 but replaced by four-cross in 2002. A team relay event was added in 1999. Mountain bike marathon was included on the schedule at the 2003 championships in Lugano, but established as a separate world championship discipline from 2004.