年龄歧视（英文：Ageism），指一种认为老年人是生理或社会方面的弱者，并因此而歧视老年人的观点，源自持有人对老年人的刻板印象。年龄歧视可以是偶然的，也可以是系统性的。这个词最早见于1969年，由美国老人学家Robert N. Butler用来描述对老年人的歧视，与性别歧视、种族歧视归纳在同一模式下。

与此同时，虽然这个词语也会用以形容对青少年及儿童的偏见和歧视，例如以他们年轻为由而忽视他们的意见，或者因为他们的年纪而设想他们应该以某种特定方式做事，不过这个词语的使用主要和对待老人的方式有关。而且，有指侮辱不一定来自大家想像中的老人群体以外，被侮辱的群体内部同样会出现这个情况。

Ageism (also spelled "agism") is stereotyping and discriminating against individuals or groups on the basis of their age. This may be casual or systematic. The term was coined in 1969 by Robert Neil Butler to describe discrimination against seniors, and patterned on sexism and racism. Butler defined "ageism" as a combination of three connected elements. Among them were prejudicial attitudes towards older people, old age, and the aging process; discriminatory practices against older people; and institutional practices and policies that perpetuate stereotypes about elderly people.