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.
| width=200 bgcolor=gold | Gold | width=200 bgcolor=silver | Silver | width=200 bgcolor=CC9966 | Bronze |
| Maciej Wyderka | Corentin le Clezio | Oussama Cherrad Zine Laggoune |
Qualification: First 3 in each heat (Q) and the next 6 fastest (q) advance to semifinal.[1]
| Rank | Heat | Name | Nationality | Time | Notes | |
|---|---|---|---|---|---|---|
| 1 | 4 | 1:49.56 | Q | |||
| 2 | 4 | 1:49.78 | Q | |||
| 3 | 4 | 1:49.85 | Q, | |||
| 4 | 4 | 1:49.94 | q | |||
| 5 | 6 | 1:49.95 | Q | |||
| 6 | 4 | 1:50.18 | q | |||
| 7 | 6 | 1:50.24 | Q | |||
| 8 | 1 | 1:50.26 | Q | |||
| 9 | 1 | 1:50.29 | Q | |||
| 10 | 4 | 1:50.31 | q | |||
| 11 | 1 | 1:50.36 | Q | |||
| 12 | 1 | 1:50.61 | q | |||
| 13 | 6 | 1:50.81 | Q | |||
| 14 | 3 | 1:51.67 | Q | |||
| 15 | 6 | 1:51.68 | q, | |||
| 16 | 3 | 1:51.73 | Q | |||
| 17 | 1 | 1:51.80 | q | |||
| 18 | 3 | 1:51.80 | Q | |||
| 19 | 5 | 1:51.84 | Q | |||
| 20 | 1 | 1:51.88 | ||||
| 21 | 3 | 1:51.97 | ||||
| 22 | 5 | 1:52.01 | Q | |||
| 23 | 2 | 1:52.14 | Q | |||
| 24 | 2 | 1:52.21 | Q | |||
| 25 | 2 | 1:52.29 | Q | |||
| 26 | 5 | 1:52.58 | Q | |||
| 27 | 3 | 1:52.73 | ||||
| 28 | 2 | 1:52.86 | ||||
| 29 | 5 | 1:54.16 | ||||
| 30 | 6 | 1:54.42 | ||||
| 31 | 6 | 1:54.54 | ||||
| 32 | 2 | 1:54.91 | ||||
| 33 | 2 | 1:56.91 | ||||
| 34 | 3 | 1:58.04 | ||||
| 35 | 5 | 1:59.12 | ||||
| 36 | 5 | 2:03.10 | ||||
| 4 | DQ | TR17.4.4 | ||||
| 5 | DQ | TR17.4.3 | ||||
| 2 | DQ | TR17.4.4 | ||||
| 3 | DQ | TR17.4.4 | ||||
| 6 | DQ | TR17.4.3 |
Qualification: First 2 in each heat (Q) and the next 2 fastest (q) advance to final.[2]
| Rank | Heat | Name | Nationality | Time | Notes | |
|---|---|---|---|---|---|---|
| 1 | 3 | 1:47.00 | Q | |||
| 2 | 1 | 1:47.19 | Q | |||
| 3 | 1 | 1:47.35 | Q | |||
| 4 | 1 | 1:47.39 | q | |||
| 5 | 1 | 1:47.40 | q, | |||
| 6 | 3 | 1:47.93 | Q | |||
| 7 | 3 | 1:47.97 | ||||
| 8 | 1 | 1:48.03 | ||||
| 9 | 2 | 1:48.08 | Q | |||
| 10 | 2 | 1:48.38 | Q | |||
| 11 | 3 | 1:48.40 | ||||
| 12 | 2 | 1:48.41 | ||||
| 13 | 3 | 1:48.71 | ||||
| 14 | 1 | 1:48.78 | ||||
| 15 | 2 | 1:48.79 | ||||
| 16 | 3 | 1:49.80 | ||||
| 17 | 2 | 1:50.47 | ||||
| 18 | 2 | 1:50.74 | ||||
| 19 | 2 | 1:54.36 | ||||
| 1 | DNF | |||||
| 3 | DNF | |||||
| 3 | DNF | |||||
| 1 | DQ | TR17.4.3PB | ||||
| 2 | DNS |
| Rank | Name | Nationality | Time | Notes | |
|---|---|---|---|---|---|
| 1:49.09 | |||||
| 1:49.17 | |||||
| 1:49.23 | |||||
| 1:49.23 | |||||
| 5 | 1:49.51 | ||||
| 6 | 1:49.65 | ||||
| 7 | 1:49.80 | ||||
| 8 | 1:49.92 |