Mary Beth Peil is an American actress and soprano. She began her career as an opera singer in 1962 with the Goldovsky Opera Theater. In 1964 she won two major singing competitions, the Young Concert Artists International Auditions and the Metropolitan Opera National Council Auditions; the latter of which earned her a contract with the Metropolitan Opera National Company with whom she performed in two seasons of national tours as a leading soprano from 1965 to 1967. She continued to perform in operas through the 1970s, notably creating the role of Alma in the world premiere of Lee Hoiby's Summer and Smoke at the Minnesota Opera in 1971. She later recorded that role for American television in 1982. With that same opera company she transitioned into musical theatre, performing the title role of Cole Porter's Kiss Me, Kate in 1983. Later that year she joined the national tour of Rodgers and Hammerstein's The King and I as Anna Leonowens opposite Yul Brynner, and continued with that production when it opened on Broadway on January 7, 1985. She was nominated for a Tony Award for her portrayal.

The King and I is the fifth musical by the team of Rodgers and Hammerstein. It is based on Margaret Landon's novel Anna and the King of Siam (1944), which is in turn derived from the memoirs of Anna Leonowens, governess to the children of King Mongkut of Siam in the early 1860s. The musical's plot relates the experiences of Anna, a British schoolteacher who is hired as part of the King's drive to modernize his country. The relationship between the King and Anna is marked by conflict through much of the piece, as well as by a love to which neither can admit. The musical premiered on March 29, 1951, at Broadway's St. James Theatre. It ran for nearly three years, making it the fourth-longest-running Broadway musical in history at the time, and has had many tours and revivals.