皮埃尔·德·费马（姓氏依发音亦作费尔玛。Pierre de Fermat，1601年8月17日－1665年1月12日，法语发音[pjɛːʀ də fɛʀma]），法国律师和业余数学家。他在数学上的成就不比职业数学家差，他似乎对数论最有兴趣，亦对现代微积分的创建有所贡献。

费马的父亲是位富有的皮革商人。费马生于塔恩-加龙省的博蒙—德洛马涅（Beaumont-de-Lomagne），出生的房子现在成了费马博物馆。1620年代中期，他进入图卢兹大学之后，搬到波尔多生活，在那里开始第一个正式的数学研究，并认识数学家Jean Beaugrand。他们之间有不少数学交流，这在费马搬到图卢兹后仍未改变。此后他又陆续认识了皮埃尔·德·卡克维、马兰·梅森和勒奈·笛卡尔等数学家，并有不少书信交流，费马的不少数学成果都在这些书信中诞生。

Pierre de Fermat (French: [pjɛːʁ dəfɛʁma]; 17 August 1601 (or 1607) – 12 January 1665) was a French lawyer at the Parlement of Toulouse, France, and a mathematician who is given credit for early developments that led to infinitesimal calculus, including his technique of adequality. In particular, he is recognized for his discovery of an original method of finding the greatest and the smallest ordinates of curved lines, which is analogous to that of the differential calculus, then unknown, and his research into number theory. He made notable contributions to analytic geometry, probability, and optics. He is best known for Fermat's Last Theorem, which he described in a note at the margin of a copy of Diophantus' Arithmetica.