希帕索斯，英文名是Hippasus，生活于大约公元前500年。发现无理数的第一人。

希帕索斯，生活于大约公元前500年，生卒年月不详，属于毕达哥拉斯学派门生。

公元前5世纪，毕达哥拉斯学派认为“万物皆数”，世界上只有整数和分数(有理数)。而希帕索斯却发现了令人震惊的“无限不循环小数”，即无理数，令该学派感到恐慌，并引发了第一次数学危机。有传言说最终希帕索斯被自己的老师毕达哥拉斯(Pythagoras)判决淹死。

Hippasus of Metapontum (/ˈhɪpəsəs/; Greek: Ἵππασος, Híppasos; fl. 5th century BC), was a Pythagorean philosopher. Little is known about his life or his beliefs, but he is sometimes credited with the discovery of the existence of irrational numbers. The discovery of irrational numbers is said to have been shocking to the Pythagoreans, and Hippasus is supposed to have drowned at sea, apparently as a punishment from the gods for divulging this. However, the few ancient sources which describe this story either do not mention Hippasus by name (e.g. Pappus) or alternatively tell that Hippasus drowned because he revealed how to construct a dodecahedron inside a sphere. The discovery of irrationality is not specifically ascribed to Hippasus by any ancient writer. Some modern scholars though have suggested that he discovered the irrationality of √2, which is believed to have been discovered around the time that he lived.