The 2005 San Marino Grand Prix was a Formula One motor race held on 24 April 2005 at the Autodromo Enzo e Dino Ferrari in Imola, Italy. The race was the fourth round of the 2005 Formula One season.

The race was won by Renault driver Fernando Alonso. Defending World Champion Michael Schumacher finished the race in second position for the Ferrari team, only two-tenths of a second behind Alonso. BAR driver Jenson Button crossed the line in third place, but his team were subsequently disqualified for underweight cars; third place was then awarded to McLaren driver Alexander Wurz.