The 2003 UCI Mountain Bike & Trials World Championships were held in Lugano, Switzerland from 31 August to 7 September 2003.
This was the first year that the cross-country marathon was included in the UCI Mountain Bike & Trials World Championships.
Anne-Caroline Chausson of France won her eighth consecutive world title in the women's downhill.
Greg Minnaar of South Africa won the world title in the men's downhill.
He thus became the first rider from the continent of Africa to win a mountain biking world championship in an elite category.