亚历山大港的丢番图（希腊语：Διόφαντος ὁ Ἀλεξανδρεύς，生卒年约公元200～214至公元284～298），有“代数之父”之称；也有人认为此称谓应与比他大约晚出生五百年的一位波斯数学家花拉子米共享。丢番图是古希腊亚历山大港的数学家，他作着的丛书《算术》（Arithmetica）处理求解代数方程组的问题，但其中有不少已经遗失。后来当法国数学家费马（Pierre de Fermat）研究《算术》一书时，对其中某个方程颇感兴趣并认为其无解，说他对此「已找到一个绝妙的证明」，但他却没有写下来，三个世纪后才出现完整的证明，详见费马大定理。在数论中常常能看到他的名字，如丢番图方程、丢番图几何、丢番图逼近等都是数学里重要的研究领域。丢番图是第一个承认分数是一种数的希腊数学家－－他允许方程中的系数和解为有理数，这是在数学史中具有开创性的。不过在今天，丢番图方程一词通常指以整数作为系数的代数方程，而其解也要求是整数。丢番图在数学符号方面也作出了贡献。

Diophantus of Alexandria (Ancient Greek: Διόφαντος ὁ Ἀλεξανδρεύς; born probably sometime between AD 201 and 215; died aged 84, probably sometime between AD 285 and 299), sometimes called "the father of algebra", was an Alexandrian Greek mathematician and the author of a series of books called Arithmetica, many of which are now lost. These texts deal with solving algebraic equations. While reading Claude Gaspard Bachet de Méziriac's edition of Diophantus' Arithmetica, Pierre de Fermat concluded that a certain equation considered by Diophantus had no solutions, and noted in the margin without elaboration that he had found "a truly marvelous proof of this proposition," now referred to as Fermat's Last Theorem. This led to tremendous advances in number theory, and the study of Diophantine equations ("Diophantine geometry") and of Diophantine approximations remain important areas of mathematical research. Diophantus coined the term παρισότης (parisotes) to refer to an approximate equality. This term was rendered as adaequalitas in Latin, and became the technique of adequality developed by Pierre de Fermat to find maxima for functions and tangent lines to curves. Diophantus was the first Greek mathematician who recognized fractions as numbers; thus he allowed positive rational numbers for the coefficients and solutions. In modern use, Diophantine equations are usually algebraic equations with integer coefficients, for which integer solutions are sought. Diophantus also made advances in mathematical notation.