食胎盘行为（英语：Placentophagy）是一种哺乳动物在自己的幼仔出生后吃掉胎盘的行为。

食胎盘行为在包括食草动物在内的有胎盘类动物中是一个普遍现象。其中仅有少量物种没有这种行为，包括鳍足类、鲸类、骆驼和人类。

学术上，对食胎盘行为的生物学机制有多种解释。有观点认为，自然界中发生的食胎盘行为主要是为了隐藏痕迹以避免遭到捕食者的追踪。但动物并不会将生产时流出的液体清理干净，仍然会留下气味而被搜索到。另一种解释是，食草动物因为妊娠生产而改变食性，变得更加嗜肉。还有观点认为动物在产前食欲下降，进食量减少，导致产后感觉饥饿或是单纯的补充能量。不过这两种观点也都存在漏洞，缺乏相关证据。

Placentophagy (from 'placenta' + Greek φαγειν, to eat; also referred to as placentophagia) is the act of mammals eating the placenta of their young after childbirth.

The placenta contains high levels of prostaglandin which stimulates involution (an inward curvature or penetration, or, a shrinking or return to a former size) of the uterus, in effect cleaning the uterus out. The placenta also contains small amounts of oxytocin which eases birth stress and causes the smooth muscles around the mammary cells to contract and eject milk. There have been very few studies that seek to prove that eating placenta provides these hormonal effects.