Teresa Mary 'Tessie' O'Shea was born on 13 March 1913 at 61 Plantagenet Street, in the Riverside district of Cardiff, to James Peter O'Shea, a newspaper wholesaler and former soldier whose parents were Irish immigrants, and his wife Nellie Theresa Carr. Raised in the British music hall tradition, she performed on stage from the age of six and made her solo debut at just 12 at the Bristol Hippodrome, billed as 'The Wonder of Wales'.
O'Shea became a much-loved variety and radio entertainer through the 1930s and 1940s, closing her act by singing and playing the banjolele in the style of George Formby. Performing in Blackpool, she adopted the theme song 'Two Ton Tessie from Tennessee', a nickname that stuck with her throughout her career. She made her American debut in the Noel Coward musical The Girl Who Came to Supper (1963), in which she played Cockney fish-and-chip seller Ada Cockle, winning the 1964 Tony Award for Best Featured Actress in a Musical.
O'Shea went on to further Broadway roles in A Time for Singing (1966), Something's Afoot (1976) and Broadway Follies (1981), and appeared in films including Bedknobs and Broomsticks (1971). Her 1968 television role in The Strange Case of Dr Jekyll and Mr Hyde earned her an Emmy Award nomination. She died on 21 April 1995 in East Lake Weir, Marion County, Florida, at the age of 82.