Theano (; Greek: Θεανώ) was a 6th-century BC Pythagorean philosopher. She has been called the wife or student of Pythagoras, although others see her as the wife of Brontinus. Her place of birth and the identity of her father is uncertain as well. Many Pythagorean writings were attributed to her in antiquity, including some letters and a few fragments from philosophical treatises, although these are all regarded as spurious by modern scholars.