The men's 800 metres event at the 2011 Military World Games was held on 19 and 20 and 22 July at the Estádio Olímpico João Havelange.
Prior to this competition, the existing world and CISM record were as follows:
| World Record | 1:41.01 | Rieti, Italy | 29 August 2010 | ||
| CISM World Record | 1:45.63 | Rome, Italy | September 1995 |
| Date | Time | Round | |
|---|---|---|---|
| 19 July 2011 | 16:40 | Round 1 | |
| 20 July 2011 | 17:40 | Semifinals | |
| 22 July 2011 | 19:00 | Final |
| width=200 bgcolor=gold | Gold | width=200 bgcolor=silver | Silver | width=200 bgcolor=CC9966 | Bronze |
| Marcin Lewandowski | Jackson Kivuva | Geoffrey Matum |
| Rank | Lane | Name | Nationality | Time | Notes | |
|---|---|---|---|---|---|---|
| 5 | 1:45.77 | |||||
| 3 | 1:45.93 | |||||
| 2 | 1:45.94 | |||||
| 4 | 6 | 1:46.69 | ||||
| 5 | 8 | 1:46.89 | ||||
| 6 | 4 | 1:46.94 | ||||
| 7 | 7 | 1:48.09 | ||||
| 8 | 1 | 1:48.13 |