CD4受体，全称“表面抗原分化簇4受体”(Cluster of Differentiation 4 receptors），是辅助T细胞的表面标记（surface markers）之一，也是辅助T细胞行使其功能的重要受体。当抗原呈递细胞（主要是巨噬细胞、棘状细胞及B细胞本身）将外来病菌分解，把抗原与主要组织兼容性复合体结合后，呈递给辅助T细胞（即与辅助T细胞表面的CD4受体结合），辅助T细胞再接着刺激B细胞产生抗体，此即体液性免疫反应的基本过程。

In molecular biology, CD4 (cluster of differentiation 4) is a glycoprotein found on the surface of immune cells such as T helper cells, monocytes, macrophages, and dendritic cells. It was discovered in the late 1970s and was originally known as leu-3 and T4 (after the OKT4 monoclonal antibody that reacted with it) before being named CD4 in 1984. In humans, the CD4 protein is encoded by the CD4 gene.