The Pythagorist Philosophers were a group of thinkers active during the Hellenistic period, from approximately the 3rd to the 1st century BCE. They belonged to the later Pythagorean tradition, which sought to revive the teachings associated with the ancient Greek sage Pythagoras after the original school had declined. Operating in an era dominated by other philosophical schools, their role was to collect, systematize, and reinterpret older Pythagorean ideas.

Their primary surviving contribution is a collection known as the "Pythagorean Memoirs" or "Commentaries." This is not a work by a single author but a compiled body of writings that attribute doctrines to early Pythagoreans. The collection itself is fragmentary, known only through quotations in later ancient authors. According to modern scholars, these Hellenistic Pythagorists often blended core Pythagorean concepts—like number theory, cosmic harmony, and the significance of opposites—with ideas from Platonism and other contemporary philosophies. To give their interpretations authority, they frequently attributed new writings to legendary early figures, a practice known as pseudepigraphy.

The historical importance of these philosophers lies in their role as preservers and transformers of the Pythagorean tradition. They provided a crucial link between early Pythagoreanism and the later revival known as Neopythagoreanism, which flourished in the Roman Empire. Their synthesized work influenced later philosophical movements, including Middle Platonism and Neoplatonism, helping to ensure that Pythagorean ideas about mathematics, cosmology, and ethics remained part of the philosophical conversation for centuries.