Valens Thessalonicus (d. ca. 261) was a Roman usurper against Roman Emperor Gallienus.
Valens was the proconsul of Achaea under Gallienus. When Macrianus rebelled to Gallienus, he met the opposition of Valens, so he sent Piso to put him to death.
It is not clear if Valens seized the imperial power to protect himself by this threat, or if the purple was imposed on him by his soldiers, but Historia Augusta reports his rise to the rank of Augustus (261). Valens defeated and killed Piso, but he was soon slain by his soldiers.
Valens is included among Trebellius Pollio's Thirty Tyrants.