Kathleen Ann Cassello (born 13 August 1958 Wilmington, Delaware USA) is an American-born opera singer. Since winning first prize in the Salzburg Mozart competition in 1985, she has toured extensively throughout Europe, Asia and North America. A graduate of the University of Delaware, she received a Bachelor of Science in Nursing degree in 1980. In the late nineties, Cassello toured with Kallen Esperian and Cynthia Lawrence as “The Three Sopranos.”