Steven Hill, who originated imposing lead roles on two notable television series, “Mission: Impossible” in the 1960s and “Law & Order” in the 1990s, died on Tuesday in Manhattan. He was 94.

His daughter Sarah Gobioff confirmed his death. He lived in Monsey, N.Y., a hamlet in Rockland County.

Mr. Hill was 44 and a veteran stage and television actor in 1966 when he was cast as Daniel Briggs, the leader of an elite covert-operations unit, in the new series “Mission: Impossible.” But he left after the first season, paving the way for Peter Graves’s six-season run as the show’s lead.

Even decades later, Mr. Hill declined to discuss his reasons for leaving the series, other than to say that the first season had been a bad experience. Other sources, including Patrick J. White, author of a book on the series, “The Complete Mission: Impossible Dossier,” said Mr. Hill was dismissed and learned the news only when he read a Daily Variety announcement that Mr. Graves was being hired.