| Agneta Mårtensson | |
| Fullname: | Ulla Agneta Linnéa Mårtensson |
| Birth Place: | Längbro, Örebro, Sweden |
| Headercolor: | lightsteelblue |
| Show-Medals: | yes |
Ulla Agneta Linnéa Mårtensson (born 31 July 1961) is a Swedish former freestyle swimmer. She won a silver medal in 4 × 100 m freestyle relay at the 1980 Summer Olympics in Moscow along with Carina Ljungdahl, Tina Gustafsson and Agneta Eriksson. She also competed in the 1984 Summer Olympics.
Mårtensson was previously married to fellow swimmer and Olympic gold medal winner Bengt Baron.