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, Melissa 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 Melissa Leo won the Golden Globe, Screen Actors Guild Award and Academy Award for Best Supporting Actress. Melissa Leo currently appears on the television series Treme.