Marianne Groat (born June 5, 1965) is a Canadian former professional tennis player.

Groat grew up in St. Catharines, Ontario and competed on the professional tour in the 1980s.

Her best performance on the WTA Tour came at the 1984 Brasil Open, where she made the quarter-finals.

At the 1985 Wimbledon Championships she featured in the main draw of the women's singles.

While at Clemson she was a member of an ACC championship team and formed a strong doubles partnership with Ingelise Driehuis, going 24–5 as a pairing in 1986.