Thor of Tranent, also known as Thor, son of Sveinn or Thor, son of Swain (fl. 1127 x 1150), Lord of Tranent and Sheriff of Lothian, was a landlord and chieftain active in Lothian in the reign of King David I of Scotland. He is attested in a large number of charters during King David's reign in Lothian, both as a charter witness on charters granted by other patrons and on charters he himself issued. His name appears either as Thor son of Sveinn or "Thor of Tranent", the latter appellation deriving from his ownership of the "barony" of Tranent, East Lothian, lands including a wide area around the modern town, including, for instance, Prestonpans.