Sir John St Aubyn, 5th Baronet

Sir John St Aubyn, 5th Baronet (17 May 1758 – 10 August 1839), was a British Member of Parliament, High Sheriff of Cornwall and Grand Master of the Freemasons.

Born in London, he succeeded to the baronetcy on 12 October 1772, at which point he inherited Clowance, the family's estate near Crowan, Cornwall.

His parents were Sir John St Aubyn, 4th Baronet, who was a Member of Parliament, and his wife, Elizabeth Wingfield; their daughter Catherine St Aubyn, two years John's junior, became an amateur artist.

He was High Sheriff of Cornwall for 1780 and was then Member of Parliament for Truro in 1784, for Penryn from 1784 to 1790, and for Helston from 1807 to 1812.

He finally married Juliana on 1 July 1822: their daughter Hebe (b.1829) was the only legitimate child of the marriage.