Mariella Greta Venter (born 10 January 2000) is a South African competitive swimmer who specializes in the backstroke. She competed in the women's 100 metre backstroke at the 2019 World Aquatics Championships.
She competed in the women's 4 x 100 metre medley relay at the 2020 Summer Olympics.
Venter competes at the collegiate level for the University of Michigan.