Margaret Sinclair may refer to:Margaret Sinclair (nun) (1900–1925), Scottish Roman Catholic nun Margaret P. Sinclair (1950–2012), Canadian mathematics educator The maiden name of Margaret Trudeau Margaret Sinclair, Countess of Caithness, see William Sinclair, 2nd Earl of Caithness Margaret Sinclair Ogden (1909–1988), American historian and lexicographer