| Toos Beumer | |
| Fullname: | Catharina Johanna Beumer |
| Birth Place: | Koog aan de Zaan, Netherlands |
| Headercolor: | lightsteelblue |
| Show-Medals: | yes |
Catharina Johanna "Toos" Beumer (born 5 July 1947 in Koog aan de Zaan) is a Dutch swimmer. She won the bronze medal in the 4×100 metres freestyle relay at the 1964 Summer Olympics in Tokyo. Her teammates in that race, clocked in 4:12.0, were Pauline van der Wildt, Erica Terpstra and Winnie van Weerdenburg. Four years later, Beumer also participated in the 1968 Summer Olympics in Mexico City, in the 100 m freestyle, but she didn't qualify for the semi-finals.[1]