| Birth Date: | 1942 4, df=yes |
| Birth Place: | Beverwijk, the Netherlands |
| Height: | 1.8m (05.9feet) |
| Weight: | 70kg (150lb) |
| Sport: | Pentathlon |
| Club: | DEM, Beverwijk |
| Show-Medals: | yes |
Marianne "Marjan" Ackermans-Thomas (born 5 April 1942) is a retired Dutch pentathlete. She competed at the 1968 Summer Olympics and finished in 17th place.