| Roles | Competed in Olympic Games • Non-starter • Referee | 
|---|---|
| Sex | Male | 
| Full name | Gunnar Erik Emanuel•Wennerström | 
| Used name | Gunnar•Wennerström | 
| Born | 27 June 1879 in Ör, Mellerud, Västra Götaland (SWE) | 
| Died | 2 June 1931 in Stockholm, Stockholm (SWE) | 
| Affiliations | Stockholms KK, Stockholm (SWE) | 
| NOC |   Sweden | 
| Medals | OG | 
| Gold | 0 | 
| Silver | 0 | 
| Bronze | 1 | 
| Total | 1 | 
| Games | Discipline (Sport) / Event | NOC / Team | Pos | Medal | As | |
|---|---|---|---|---|---|---|
| 1906 Intercalated Games | Swimming (Aquatics) |  SWE | 
Gunnar Wennerström | |||
| 100 metres Freestyle, Men (Intercalated) | ||||||
| 400 metres Freestyle, Men (Intercalated) | ||||||
| 1 mile Freestyle, Men (Intercalated) | ||||||
| 1908 Summer Olympics | Swimming (Aquatics) |  SWE | 
Gunnar Wennerström | |||
| 400 metres Freestyle, Men (Olympic) | ||||||
| 1,500 metres Freestyle, Men (Olympic) | 2 h1 r1/3 | |||||
| 4 × 200 metres Freestyle Relay, Men (Olympic) | Sweden | 3 h2 r1/2 | ||||
| Water Polo (Aquatics) |  SWE | 
Gunnar Wennerström | ||||
| Water Polo, Men (Olympic) | Sweden | 3 | Bronze | 
| Games | Sport (Discipline) / Event | NOC / Team | Phase | Unit | Role | As | |
|---|---|---|---|---|---|---|---|
| 1912 Summer Olympics | Water Polo (Aquatics) |  SWE | 
Gunnar Wennerström | ||||
| Water Polo, Men (Olympic) | Match #3 | Austria — Hungary | Referee | ||||
| Water Polo, Men (Olympic) | Match #1 | Great Britain — Sweden | Referee | ||||
| Water Polo, Men (Olympic) | Match #1 | Belgium — Hungary | Referee | ||||
| Water Polo, Men (Olympic) | Match #2 | Belgium — France | Referee | ||||
| Water Polo, Men (Olympic) | Match #1 | Great Britain — Belgium | Referee |