Margaret Valerie Masterson is a retired English opera singer, a lecturer and Vice-President of British Youth Opera. After study in Italy, she began to sing opera in Europe. Returning to England, Masterson performed as principal soprano with the D'Oyly Carte Opera Company from 1964 to 1969, becoming popular with audiences and participating in several of the company's recordings, as well as those of Gilbert and Sullivan for All and the BBC.

The D'Oyly Carte Opera Company is a professional British light opera company that, from the 1870s until 1982, staged Gilbert and Sullivan's Savoy operas nearly year-round in the UK and sometimes toured in Europe, North America and elsewhere. The company was revived for short seasons and tours from 1988 to 2003, and since 2013 it has co-produced four of the operas with Scottish Opera.