| Strokes: | Freestyle |
| Club: | Stockholms KK |
| Birth Date: | 18 December 1884 |
| Birth Place: | Stockholm, Sweden |
| Death Date: | 14 November 1950 (aged 65) |
| Death Place: | Jersey City, New Jersey, United States |
| Height: | 170 cm |
| Show-Medals: | yes |
Nils Gustaf Regnell (18 December 1884 – 14 November 1950) was a Swedish freestyle swimmer. He competed at the 1906 Intercalated Games in the one mile and 4×250 m events and finished fifth in the relay. His younger sisters Elsa and Lisa were Olympic divers.