葡萄糖-6-磷酸脱氢酶（英语：glucose-6-phosphate dehydrogenase，EC 1.1.1.49）是一种以NAD或NADP为受体、作用于供体CH-OH基团上的氧化还原酶。这种酶能催化以下酶促反应：

葡萄糖-6-磷酸脱氢酶主要参与磷酸戊糖途径，也能缓慢地作用在β-D-葡萄糖等其他糖类上。这种酶可由其底物葡萄糖-6-磷酸激活，如果人类表达葡萄糖-6-磷酸脱氢酶的基因G6PD有缺陷，将会导致葡萄糖-6-磷酸脱氢酶缺乏症，引发非免疫性溶血性贫血。葡萄糖-6-磷酸脱氢酶存在于众多生物细胞内，高等植物拥有数种葡萄糖-6-磷酸脱氢酶的蛋白异构体（protein isoform），它们分布于细胞质基质、和过氧化物酶体等细胞结构中。

Glucose-6-phosphate dehydrogenase (G6PD or G6PDH) (EC1.1.1.49) is a cytosolic enzyme that catalyzes the chemical reaction

This enzyme participates in the pentose phosphate pathway (see image), a metabolic pathway that supplies reducing energy to cells (such as erythrocytes) by maintaining the level of the co-enzyme nicotinamide adenine dinucleotide phosphate (NADPH). The NADPH in turn maintains the level of glutathione in these cells that helps protect the red blood cells against oxidative damage from compounds like hydrogen peroxide. Of greater quantitative importance is the production of NADPH for tissues actively engaged in biosynthesis of fatty acids and/or isoprenoids, such as the liver, mammary glands, adipose tissue, and the adrenal glands. G6PD reduces NADP to NADPH while oxidizing glucose-6-phosphate.