表皮是人和动物皮肤的外层，由胚胎时期外胚层形成。

在多细胞无脊椎动物，一般为单层细胞，其表面有细胞分泌的角质膜或外骨骼，起到保护作用，如蠕虫的角质膜和节肢动物的外骨骼。原索动物如文昌鱼的表皮仍为单层细胞。脊椎动物则都为复层上皮组织，通常水生脊椎动物只有几层生发层，陆生脊椎动物由于适应陆生环境，最外面的表皮细胞分化出角质层，起到保护和防止体液丢失。

表皮由角质层、透明层、颗粒层、棘层和zh:生发层所组成，内无血管，但有游离神经末稍。

The epidermis is composed of the outermost layers of cells in the skin, "epi" in Greek meaning "over" or "upon", which together with the dermis forms the cutis.

The epidermis is a stratified squamous epithelium, composed of proliferating basal and differentiated suprabasal keratinocytes which acts as the body's major barrier against an inhospitable environment, by preventing pathogens from entering, making the skin a natural barrier to infection. It also regulates the amount of water released from the body into the atmosphere through transepidermal water loss (TEWL).