脉络膜（Choroid）是位于视网膜和巩膜之间的组织，主要由色素及微细血管组成，呈暗褐色。其血管供给视网膜葡萄糖及氧气。色素则吸收眼球内多余的光，防止它们因折射和散射而干扰视细胞作用的精确度。

脉络膜提供氧气和营养素到视网膜的外层并把废物运走，因含有丰富的色素，故脉络膜有遮光作用，亦能够防止眼球内部光线反射。

The choroid, also known as the choroidea or choroid coat, is the vascular layer of the eye, containing connective tissue, and lying between the retina and the sclera. The human choroid is thickest at the far extreme rear of the eye (at 0.2 mm), while in the outlying areas it narrows to 0.1 mm. The choroid provides oxygen and nourishment to the outer layers of the retina. Along with the ciliary body and iris, the choroid forms the uveal tract.