Mateusz Demczyszak (born January 18, 1986) is a Polish middle distance runner.
| Year | Competition | Venue | Position | Event | Notes |
|---|---|---|---|---|---|
| Representing Poland | |||||
| 2005 | European Junior Championships | Kaunas, Lithuania | 5th | 3 000 m steeplechase | 8:57.24 |
| 2010 | European Championships | Barcelona, Spain | 8th | 1500 m | 3:44.42 |