Margaret Christian "Peggy" Jay, Baroness Jay (née Garnett; 4 January 1913 – 21 January 2008) was an English Labour member of London County Council and the Greater London Council between 1934, when she was still in her twenties, and 1967. She then chaired the Heath and Old Hampstead Society from 1967 to 1989. In 1981 she joined the Social Democratic Party, but in 2007 returned to Labour.