质体醌（英语：Plastoquinone，简称：PQ）是一种醌分子，与光合作用中光反应的电子传递链有关。质体醌被还原（得到叶绿体基质中的两个质子（H），并与来自光系统II的两个电子（e）相结合），形成质体酚。它承载质子进入类囊体盘腔，电子于此通过电子传递链进入细胞色素b₆f蛋白质复合体。

前缀plasto-意为质体或叶绿体，反映了其在细胞中的位置。

它的结构为一个2,3-二甲基-1,4-苯醌分子，侧链有9个异戊二烯基单元。

Plastoquinone (PQ) is a quinone molecule involved in the electron transport chain in the light-dependent reactions of photosynthesis. Plastoquinone is reduced when it accepts two electrons from photosystem II and two hydrogen cations (H) from the stromal matrix of the chloroplast), thereby forming plastoquinol. It transports the protons into the lumen of thylakoid discs, while the electrons continue further along the electron transport chain, into the cytochrome b₆f protein complex.