The men's 800 metres event at the 2021 Summer World University Games was held on 4, 5 and 6 August 2023 at the Shuangliu Sports Centre Stadium in Chengdu, China.
Qualification: First 3 in each heat (Q) and the next 6 fastest (q) advance to semifinal.
Qualification: First 2 in each heat (Q) and the next 2 fastest (q) advance to final.