Catherine St Aubyn (1760 - 1836) was a Cornish amateur artist.
Catherine St Aubyn was born in 1760, she was the daughter of Sir John St Aubyn, 4th Baronet of Clowance in Cornwall. Her brother was the M.P. and fossil collector Sir John St Aubyn, 5th Baronet. St Aubyn's father was a friend and patron of the painter John Opie and he arranged for Catherine to have lessons. Her work is rare but there are a few of her works at St Michael's Mount.
She married on 26 June 1790 her cousin the Reverend John Molesworth who was the rector of St Breock in Cornwall. Her son inherited the St Aubyn estates and she died in 1836.