Margaret Sheila Mackellar Chisholm (9 September 1895 – 13 October 1969) was an Australian socialite and "it girl" in British high society during and after World War I.
She married three times: Francis St Clair-Erskine, Lord Loughborough (heir to the 5th Earl of Rosslyn); Sir John Charles Peniston Milbanke, 11th Bt; and Prince Dmitri Alexandrovich of Russia.
Chisholm also had close relationships with brothers George VI and Edward VIII, both future Kings of the United Kingdom.
Chisholm's romantic liaison with George ended when his father, George V, told him to leave the already-married Australian and find someone more suitable.
Known for her striking beauty, she is likely the inspiration for the Australian phrase "a good-looking sheila".