Oanh Thi "Cecilia" Bui, written in Vietnamese as "Bùi Oanh Thị", and known by the stage name Lệ Thu (July 16, 1943 – January 15, 2021), was a Vietnamese singer. Born in Hải Phòng, she was well known in South Vietnam in the 1960s and 1970s for singing the songs of singer-songwriters such as Trịnh Công Sơn and Phạm Duy. She released 24 singles and numerous albums with famous overseas Vietnamese singers like Khánh Ly, Hương Lan and Tuấn Ngọc.