Walter Slezak (May 3, 1902 – April 21, 1983) was an Austrian actor. Slezak often portrayed villains or thugs, notably the German U-boat commander in Alfred Hitchcock's 1944 Lifeboat, but occasionally he played lighter, kindlier roles, as in The Wonderful World of the Brothers Grimm and as Squire Trelawney in Treasure Island.
His first American film was 1942's Once Upon a Honeymoon, opposite Ginger Rogers and Cary Grant. He worked steadily and appeared in over 100 films including The Princess and the Pirate, The Spanish Main, Sinbad the Sailor, Born to Kill, Call Me Madam, and Treasure Island.
Slezak acted in radio in such shows as Lux Radio Theater, Columbia Workshop, The Pepsodent Show, and The Charlie McCarthy Show. He made numerous television appearances, including Playhouse 90 and Studio One, and he appeared as "The Clock King" on Batman in 1966.
His autobiography, What Time's the Next Swan? was published in 1962. The book's title refers to an alleged incident in the career of his father, heldentenor Leo Slezak. During a performance in the title role of Lohengrin, the elder Slezak was supposed to finish his aria by stepping into a swan boat and then being pulled offstage. When a stagehand removed the boat prematurely, Slezak supposedly covered for the error by asking the audience "What Time's the Next Swan?".
On April 21, 1983, shortly before his 81st birthday, Slezak died from a self-inflicted gunshot wound. Slezak was reportedly despondent over his advanced physical illness. He is buried at Egern Friedof in Munich, Germany.