Ecphantus or Ecphantos (Ancient Greek: Ἔκφαντος) or Ephantus (Έφαντος) was an Ancient Greek pre-Socratic philosopher. He is identified as a Pythagorean of the 4th century BCE from Syracuse, Magna Graecia, but the details concerning his life are historically obscure; he may have not been a historical person, but rather a fictional character invented by Heraclides of Pontus for use in his philosophical dialogues.^[1] He also may have been the same figure as the attested Ecphantus of Croton.^{[citation needed]}Ecphantus was also of Syracuse. He developed a theory about constellations moving.

According to Eusebius, Ecphantus, like Heraclides of Pontus, was a supporter of the heliocentric theory: he believed that the Earth turns around its centre from west to towards east, like a wheel, as if it has an axis, the state.^[2] Ecphantus also maintained that there is only one Cosmos (Universe) governed by providence (πρόνοια).