Joan Humphrey Lefkow (born January 9, 1944) is a United States district court senior judge for the Northern District of Illinois. She was nominated by President Bill Clinton on May 11, 2000, to a seat vacated by Judge Ann Claire Williams, and confirmed by the United States Senate on June 30, 2000. Lefkow received her commission on July 11, 2000. On September 1, 2012, Lefkow assumed senior status.