Melissa Chessington Leo (born September 14, 1960), also known as Margaret May II or Margaret May, is an American actress. After appearing on several television shows and films in the late '80s, her breakthrough role came in 1993 as Det. Sgt. Kay Howard on the television series Homicide: Life on the Street for the show's first five seasons from 1993–1997. Having previously been a regular on All My Children and The Young Riders, her breakthrough film role was in the 2003 film, 21 Grams.
Following several films, Leo received critical acclaim and national attention in the 2009 film, Frozen River earning several nominations and awards, including an Oscar nomination for Best Actress. In 2011, Leo earned several awards for her role as Alice Ward in the critically acclaimed film, The Fighter. For this role Leo won the Golden Globe, Screen Actors Guild Award and Academy Award for Best Supporting Actress. Leo currently appears on the television series Treme.
Leo was born in Manhattan, New York City, New York, the daughter of Peggy (née Chessington), a California-born teacher, and Arnold Leo, an editor at Grove Press, fisherman, and spokesman for the East Hampton Baymen's Association. Leo was raised on the Lower East Side of Manhattan and spent summers at her father's house in Springs, a section of East Hampton, N.Y. She is a former resident of Putney, Vermont and now lives in Stone Ridge, New York. She has a son with actor and former boyfriend John Heard named John Matthew Heard (born 1987) and years later adopted Adam (born 1984).