The 2003 Giro d'Italia was the 86th edition of the Giro d'Italia, one of cycling's Grand Tours. The Giro began in Lecce with a 201 km (125 mi) mass-start stage. The race came to a close with a 33 km (21 mi) individual time trial that began and ended in the Italian city of Milan. Nineteen teams entered the race that was won by the Italian Gilberto Simoni of the Saeco team. Second and third were the Italian Stefano Garzelli and Ukrainian Yaroslav Popovych.

The Giro d'Italia is an annual multiple-stage bicycle race primarily held in Italy, while also starting in, or passing through, other countries. The first race was organized in 1909 to increase sales of the newspaper La Gazzetta dello Sport, and the race is still run by a subsidiary of that paper's owner. The race has been held annually since its first edition in 1909, except during the two world wars. As the Giro gained prominence and popularity, the race was lengthened, and the peloton expanded from primarily Italian participation to riders from all over the world. The Giro is a UCI World Tour event, which means that the teams that compete in the race are mostly UCI WorldTeams, with some additional teams invited as 'wild cards'.