Joannes Philoponus (also known as "John the Grammarian") was a Greek philosopher of Alexandria who lived in the later part of the 5th century and the beginning of the 6th century. The surname Grammaticus he assumed in virtue of his lectures on language and literature; that of Philoponus owing to the large number of treatises he composed. He was a pupil of Ammonius Hermiae, and is supposed to have written the life of Aristotle sometimes attributed to his master. To Philoponus are attributed a large number of works on theology and philosophy. It is said that, though he was a pupil of Ammonius, he was at first a Christian,, and he has been credited with the authorship of a commentary on the Mosaic Cosmogony in eight books, dedicated to Sergius, patriarch of Constantinople, and edited by Balthasar Corderius in 1630. Other authorities maintain that this, as well as the Disputalio de paschale, was the work of another author, John the Tritheist.

The more certain writings of Philoponus consist of commentaries on Aristotle. These include works on the Physica, the Prior and the Posterior Analytics, the Meteorologica, the De anima, the De generations animatium, the De generatione et interitu and the Metaphysica. These have been frequently edited and are interesting in connection with the adoption of Aristotelianism by the Christian Church. They seem to have embodied the lectures of Ammonius with additions by Philoponus, and are remarkable rather for elaborate care than for originality and insight. He also wrote an attack on Proclus (De aeternitate mundi). Two treatises on mathematics are ascribed to him: A Commentary on the Mathematics of Nicomachus, edited by Hoche (1864 and 1867), and a Treatise on the Use of the Astrolabe, published by Hase. The latter is the most ancient work on this instrument, and its authenticity is rendered almost certain by its reference to Ammonius as the master of the author.

This article incorporates text from the public domain 1911 Encyclopædia Britannica.