Barbara Stanisława "Basia" Trzetrzelewska 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 beginning in the late 1960s and during the 1970s, then moved 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 left the group to focus on her solo career. She signed with Epic Records and enjoyed a successful international career from 1987 until 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 include "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. She made a comeback to regular recording and performing beginning with the release of the Matt Bianco reunion album Matt's Mood in 2004. She now releases her music through independent labels.