永恒轮回（或作永恒循环、永恒重现或永劫回归）指一种假定宇宙会不断，而且将会以完全相同的形式循环的观念，而且这种循环的次数不可理解，也无法预测。

永恒轮回的观念发源于古埃及时代，也是印度哲学的重要部分，在印度教和佛教中表现为轮回理论。

在古希腊，毕氏学派和斯多葛学派等也接受和发展了类似观点。

一些中美洲文明（如玛雅和阿兹特克）也将轮回视为其哲学和宗教中的核心观念。

在西方，随着古典文明的没落及基督教的崛起，永恒轮回的观念被基督教神学世界观所取代，即世界始于耶和华创世，并终于最后审判后归于时间上无尽的天国。19世纪中期，欧洲物理学家认为如果时空无限，则相同形式的物质必然无限次重复。叔本华在其著作中发展了这一观点，但仅视之为物理概念，即物质以同一形式反复出现于循环性的时间。尼采对永恒轮回的概念进行了哲学反思，从而使这一概念再度复兴于西方哲学。

Eternal return (also known as "eternal recurrence") is a concept that the universe and all existence and energy has been recurring, and will continue to recur, in a self-similar form an infinite number of times across infinite time or space. The concept is found in Indian philosophy and in ancient Egypt and was subsequently taken up by the Pythagoreans and Stoics. With the decline of antiquity and the spread of Christianity, the concept fell into disuse in the Western world, with the exception of Friedrich Nietzsche, who connected the thought to many of his other concepts, including amor fati.