忒修斯（希腊语：Θησεύς；拉丁文：Theseus），又译作特修斯、提修斯等，传说中的雅典国王。纪德的长篇小说《忒修斯》即以其为主人公。他的事迹主要有：翦除过很多著名的强盗；解开米诺斯的迷宫，并战胜了弥诺陶洛斯；和希波吕忒结婚；劫持海伦，试图劫持冥王哈得斯（罗马神话作“普路托”）的妻子珀耳塞福涅——因此被扣留在冥界，后来被海格力斯救出。据说其在位期间（约公元前9世纪---公元前8世纪,一说为公元前13世纪中叶）进行了改革，主要完成了两件事：一、把4个阿提卡部落联合成为一个阿提卡国家，建造了雅典卫城，设立了唯一的公共议事会厅，定国名为雅典。二、把全体居民分为贵族、农民、手工业者3个等级。

Theseus (/ˈθiːsiːəs/; Ancient Greek: Θησεύς [tʰɛːsěu̯s]) was the mythical king of Athens and was the son of Aethra by two fathers: Aegeus and Poseidon.

Theseus was a founder-hero, like Perseus, Cadmus, or Heracles (Hercules), all of whom battled and overcame foes that were identified with an archaic religious and social order. As Heracles was the Dorian hero, Theseus was a founding hero, considered by Athenians as their own great reformer: his name comes from the same root as θεσμός ("thesmos"), Greek for "The Gathering". The myths surrounding Theseus—his journeys, exploits, and family—have provided material for fiction throughout the ages.