Euclid (mathematician), (lived circa 300 bc), Greek mathematician, whose chief work, Elements, is a comprehensive treatise on mathematics in 13 volumes on such subjects as plane geometry, proportion in general, the properties of numbers, incommensurable magnitudes, and solid geometry. He probably was educated at Athens by pupils of Plato. He taught geometry in Alexandria and founded a school of mathematics there. The Data, a collection of geometrical theorems; the Phenomena, a description of the heavens; the Optics; the Division of the Scale, a mathematical discussion of music; and several other books have long been attributed to Euclid; most historians believe, however, that some or all of these works (other than the Elements) have been spuriously credited to him. Historians disagree as to the originality of some of his other contributions. Probably the geometrical sections of the Elements were primarily a rearrangement of the works of previous mathematicians such as those of Eudoxus, but Euclid himself is thought to have made several original discoveries in the theory of numbers (see Number Theory).

Euclid's Elements was used as a text for 2000 years, and even today a modified version of its first few books forms the basis of high school instruction in plane geometry. The first printed edition of Euclid's works was a translation from Arabic to Latin, which appeared at Venice in 1482.