| Competition: | Mestaruussarja |
| Season: | 1931 |
| Winners: | HIFK Helsinki |
| Relegated: | HJK Helsinki ViPS Viipuri |
| Matches: | 56 |
| Total Goals: | 136 |
| League Topscorer: | Holger Salin, HIFK Helsinki (11) |
| Prevseason: | 1930 |
| Nextseason: | 1932 |
The 1931 season was the second completed season of Finnish Football League Championship, known as the Mestaruussarja. HIFK Helsinki is the defending champion.
The 1931 Mestaruussarja was contested by 8 teams, with HIFK Helsinki winning the championship which was also known as the A-sarja [‘A-Series’]. HJK Helsinki and ViPS Viipuri were relegated to the second tier which was known as the B-sarja [‘B-Series’].
In 1930, there were 8 participants in the Mestaruussarja: