Theodorus of Samos (Greek: Θεόδωρος ὁ Σάμιος) was a 6th-century BC ancient Greek sculptor and architect from the Greek island of Samos. Along with Rhoecus, he was often credited with the invention of ore smelting and, according to Pausanias, the craft of casting. He is also credited with inventing a water level, a carpenter's square, and, according to Pliny, a lock and key and the turning lathe. According to Vitruvius (vii, introduction), Theodorus is the architect of the Doric Order temple Heraion of Samos temple. In some texts he is described, above all, as a great artist and in some statues he is depicted as a great inventor.