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Robert Recorde (c. 1510 – 1558) was a Welsh physician and mathematician. He introduced the "equals" sign (=) in 1557.

A member of a respectable family of Tenby, Wales, he entered the University of Oxford in about 1525, and was elected a fellow of All Souls College in 1531. Having adopted medicine as a profession, he went to the University of Cambridge to take the degree of M.D. in 1545. He afterwards returned to Oxford, where he publicly taught mathematics, as he had done prior to going to Cambridge. It appears that he afterwards went to London, and acted as physician to King Edward VI and to Queen Mary, to whom some of his books are dedicated. He was also controller of the Royal Mint and served as "Comptroller of Mines and Monies" in Ireland.[1] After being sued for defamation by a political enemy, he was arrested for debt and died in the King's Bench Prison, Southwark, in 1558.

Recorde published several works upon mathematical subjects, chiefly in the form of dialogue between master and scholar, such as the following:

* The Grounde of Artes, teachings the Worke and Practise, of Arithmeticke, both in whole numbers and fractions (c. 1540), the first English book on algebra.
* The Pathway to Knowledge, containing the First Principles of Geometry ... bothe for the use of Instrumentes Geometricall and Astronomicall, and also for Projection of Plattes (London, 1551)
* The Castle of Knowledge, containing the Explication of the Sphere both Celestiall and Materiall, etc. (London, 1556)
* The Whetstone of Witte, whiche is the seconde parte of Arithmeteke: containing the extraction of rootes; the cossike practise, with the rule of equation; and the workes of Surde Nombers (London, 1557). This was the book in which the equals sign was introduced. With the publication of this book Recorde is credited with introducing algebra into England.[2]
* a medical work, The Urinal of Physic (1548), frequently reprinted.

Sherburne states that Recorde also published Cosmographiae isagoge, and that he wrote a book De Arte faciendi Horologium and another De Usu Globorum et de Statu temporum. Recorde's chief contributions to the progress of algebra were in the way of systematizing its notation.