Mary Nell Steenburgen (born February 8, 1953) is an American actress and occasional singer. She won the Academy Award for Best Supporting Actress and Golden Globe Award for Best Supporting Actress for playing the role of Lynda Dummar in Jonathan Demme's 1980 film Melvin and Howard.

Steenburgen, who studied at New York's Neighborhood Playhouse in the 1970s, also received a Golden Globe nomination for the 1981 film Ragtime, a BAFTA TV Award nomination for the 1985 miniseries Tender is the Night and an Emmy Award nomination for the 1988 TV film The Attic: The Hiding of Anne Frank. Her other film appearances include Cross Creek (1983), Parenthood (1989), Back to the Future Part III (1990), Philadelphia (1993), What's Eating Gilbert Grape (1993), Elf (2003), The Brave One (2007), Step Brothers (2008), The Proposal (2009), and The Help (2011).