Nancy Justine McKeon (born April 4, 1966) is an American actor. She was born in Westbury, New York.

She was born into a show business family; she and her brother Philip McKeon did numerous commercials. Nancy also appeared on the soap operas The Secret Storm and Another World.

The McKeons moved to Los Angeles in 1975, when Philip got a job as Linda Lavin's son on the television series Alice. In 1979, Nancy was discovered by a casting director for The Facts of Life after a performance in a Hallmark greeting cards advertisement.

She was cast as tomboy Jo Polniaczek on the sitcom, and debuted on the show in the fall of 1980. This would be Nancy's most famous role; she would play it until the show was canceled in 1988.

Since then, she has starred in many made-for-TV movies, most notably A Cry for Help: The Tracey Thurman Story, in which she portrays an abuse victim. She starred in her own series, Can't Hurry Love, in 1995, to only lukewarm success. Since 2001, she has played Inspector Jinny Exstead on the Lifetime drama The Division. Previously, she starred in the movie The Wrong Woman, as a woman framed for killing her boss.

She married key grip Marc Andrus in June 2003, and in March 2004 gave birth to her daughter, Aurora.