Barbara Stanisława "Basia" Trzetrzelewska (Polish: [ˈbaɕa tʂɛtʂɛˈlɛfska] ; born 30 September 1954), better known mononymously as Basia, is a Polish singer-songwriter and recording artist noted for her Latin-inspired jazz-pop music.

She began singing professionally in various Polish bands from the late 1960s throughout the 1970s, then relocated to the UK in 1981. She rose to fame as a singer in the British trio Matt Bianco. By 1986, Basia and her bandmate Danny White had left the group to focus on her solo career.

She signed on with Epic Records and enjoyed a successful international career between 1987 and 1995, particularly in the US where her first two albums Time and Tide and London Warsaw New York both sold more than a million copies, her biggest hits being "Time and Tide", "New Day for You", "Promises", "Baby You're Mine", "Cruising for Bruising", and "Drunk on Love". She also developed a following in Asia.

She took a lengthy hiatus due to personal tragedies, then made a comeback to regular recording and performing in the late 2000s. She currently releases her music through independent labels.