Robert Vaughn, the cleft-chinned actor who reached the peak of his fame in the 1960s playing Napoleon Solo, the debonair international agent tasked with saving the world each week on the hit television series “The Man From U.N.C.L.E.,” died on Friday in Danbury, Conn. He was 83.

His manager, Matthew Sullivan, said that the cause was acute leukemia, for which Mr. Vaughn had been under treatment in Manhattan and Connecticut.

Mr. Vaughn had numerous roles in film and on television. He played an old boyfriend of Laura Petrie (Mary Tyler Moore) on an episode of “The Dick Van Dyke Show” and a gunman in “The Magnificent Seven” (1960). He was nominated for an Academy Award as best supporting actor for his role as a man accused of murder in “The Young Philadelphians” (1959) and won an Emmy in 1978 for his performance as a White House chief of staff in the mini-series “Washington: Behind Closed Doors.”

But no character he played was as popular as Napoleon Solo. From 1964 to 1968, in the thick of the Cold War, millions of Americas tuned in weekly to “The Man From U.N.C.L.E.” to watch Mr. Vaughn, as a superagent from the United Network Command for Law and Enforcement, battling T.H.R.U.S.H. (Technological Hierarchy for the Removal of Undesirables and the Subjugation of Humanity), a secret organization intent on achieving world domination through nefarious if far-fetched devices like mind-controlling gas.