John Victor Shea III ( SHAY; born April 14, 1949) is an American actor, film producer and stage director. His career began on Broadway where he starred in Yentl, subsequently winning his first major award, the 1975 Theatre World Award. Shortly after his Off-Broadway career began, Lee Strasberg invited Shea to join the Actors Studio where he spent several years studying method acting.

He made his television film debut in The Nativity (1978), alongside Madeleine Stowe. Billed alongside Helen Mirren, he starred in the noir film Hussy (1980) and the Academy Award-winning drama Missing (1982). In 1988, Shea won his first Emmy for his performance as William Stern in Baby M. Shea's subsequent films include the comedy thriller Coast to Coast (1987), the drama Windy City (1984), the dark crime feature Small Sacrifices (1989), the political thriller The Insurgents (2006), the Tamil language thriller Achchamundu! Achchamundu! (2009), the drama An Invisible Sign (2010), and the Finnish film The Italian Key (2011).

His breakthrough came when he was cast as Lex Luthor in the 1990s TV series Lois & Clark: The New Adventures of Superman, subsequently being cast as Adam Kane in the 2000s Mutant X series. Shea's public profile increased in 2012 after his five-year role as Harold Waldorf, Blair Waldorf's father on Gossip Girl.

Shea has been noted for his political involvement in social equity, which in 1984 led him to organize the largest peace rally in the history of the United States, garnering praise by various non-governmental organizations such as Amnesty International. In 2014, Shea announced his directorial debut with Grey Lady, released in mid-2017.