John Karlen was an American actor.

Karlen, who studied at the American Academy of Dramatic Arts and began his career on stage, appeared in the 1959 Broadway production of Tennessee Williams' Sweet Bird of Youth.

From the late 1950s until the mid-1990s, Karlen worked almost constantly in television, amassing well over 100 acting credits. In 1967, Karlen joined the cast of ABC's gothic soap opera Dark Shadows, playing doomed con man Willie Loomis, among several other characters, and remained with the series until its conclusion in 1971.

Karlen also made appearances on episodes of Night Gallery, Mod Squad, Mannix, Hawaii Five-0, The Waltons, All in the Family, Charlie's Angels, Kojak, The Rockford Files, Starsky and Hutch, Lou Grant, Quincy, M.E., Fame, Hill Street Blues, Mad About You, and Murder, She Wrote.

Karlen was a three-time Emmy Award nominee (in 1985, '86, and '87) for his role as Harvey Lacey, husband of Detective Mary Beth Lacey (Tyne Daly) on the CBS drama series Cagney & Lacey, winning in 1986. He reprised the role in several Cagney & Lacey made-for-TV movies in the 1990s.

Karlen died January 22, 2020, in Burbank, California. He was 86.