Sir John Stepney, 8th Baronet (1743–1811), of Llanelli, Carmarthenshire, was a Welsh politician.
He was born the first son of Sir Thomas Stepney, 7th Bt., of Llanelly and educated at Christ Church, Oxford (1760). He succeeded his father as 8th Baronet in 1772.
He was a Member (MP) of the Parliament of Great Britain for Monmouth Boroughs from 1767 to 1788.
He died unmarried in Trnava, Hungary in 1811. He was succeeded to the baronetcy by his brother Thomas, but left his estate to his illegitimate child, William Chambers.