The 2003 UCI Road World Championships took place in Hamilton, Ontario, Canada, between October 7 and October 12, 2003. The event consisted of a road race and a time trial for men, women, men under 23, junior men and junior women.

David Millar was handed a two-year ban and stripped of his world time trial title by the British cycling federation for taking the banned performance enhancer EPO. Following this disqualification, the UCI declared Michael Rogers as the winner with the silver medal going to Uwe Peschel and the bronze to Michael Rich.

Jeannie Longo rode alone ahead of the pack for most of the women's road race but was passed approximately 500m from the finish.

The road races took place on a 12 kilometres (7.5 mi) course that climbed the Niagara Escarpment twice per lap – a 1.6 km (0.99 mi) climb with an average gradient of 4.9% and a 2.5 km (1.6 mi) climb with an average gradient of 4.2%.

Two time trial courses were used – a 21 kilometres (13 mi) course that climbed the Niagara Escarpment on two occasions, and a 15 kilometres (9.3 mi) course that climbed the Niagara Escarpment once.

The courses had been designed by former professional cyclist Steve Bauer.