The 2021 6 Hours of Monza was an endurance sports car racing event held at Autodromo Nazionale di Monza, Monza, Italy, on 18 July 2021.

It served as the third round of the 2021 FIA World Endurance Championship and was the first running of the event as part of the championship.

Pole position winners in each class are marked in bold.

[1] The minimum number of laps for classification (70% of the overall winning car's race distance) was 142 laps.

Class winners are denoted in bold and with ‡.