He was born Cyril Joseph Trimnell-Ritchard in Surry Hills, Sydney, New South Wales, to Sydney-born parents, Herbert Trimnell-Ritchard, a Protestant grocer, and his wife Marguerite, a devout Roman Catholic who ensured her son was raised as a Roman Catholic. Educated by the Jesuits at St Aloysius' College, Cyril was a lifelong devout Catholic who attended Sunday Mass wherever he happened to be.
He achieved star status in 1954 as Captain Hook in the Broadway production of Peter Pan co-starring Mary Martin, with whom he shared the same birthday (1 December). For his work in the show, Ritchard received a Tony Award as Best Featured Actor in a Musical. Both Ritchard and Martin reprised their roles in the NBC television productions of the musical, beginning with a live color telecast in 1955. In 1959 he won second Tony Award for Best Actor in a Play for "The Pleasure of His Company"
Ritchard also appeared regularly on a variety of television programs in the late 1950s and 1960s. For example, he did a stint as one of the What's My Line? mystery guests on 22 December 1957, episode of the popular Sunday night CBS-TV program. In the 1950s Ritchard played the comic lead in Jacques Offenbach's operetta, La Perichole at the Metropolitan Opera in New York City. Later Ritchard served as a guest panelist on the Met's radio quiz show, where he was, perhaps comically, referred to as 'Sir Cyril'. However, Ritchard was never knighted.
A memorable television out-take features Ritchard saying 'Goodnight' to an audience, before spinning a ball on a roulette wheel. Ritchard watches as the ball rattles around the wheel, seemingly interminably, before it finally bounces off the wheel, hits the spindle and flies off-screen.
Shortly before he died, Ritchard performed as the voice of Elrond in the Rankin/Bass television production of The Hobbit. Ritchard lived at The Langham, a famed apartment house in New York. He suffered a heart attack on 25 November 1977, aged 78, while appearing as the narrator in the Chicago touring company of Side by Side by Sondheim. He died nearly a month later in Chicago, aged 79, and was buried at Saint Mary's Cemetery in Ridgefield, Connecticut, where he had long resided in his rural home. His funeral Mass was celebrated by Archbishop Fulton Sheen. His wife Madge predeceased him in 1955 as did a baby boy who died in infancy in 1939.