视网膜母细胞瘤蛋白（英语：retinoblastoma protein，常缩写为Rb、RB或RB1）又译为成视网膜细胞瘤蛋白是一种抑癌蛋白，并在几种主要的癌症发生时失活。Rb的功能之一是通过抑制细胞周期进程直到细胞准备妥当来防止细胞过度生长。当细胞准备好要分裂时，Rb蛋白会被磷酸化为pRb而失去抑制活性，从而使细胞周期进行下去。

Rb是袋状蛋白家族的一员，其特点是有一个口袋状的结构用以结合其它蛋白。使得一些致癌变蛋白，比如高危险群人类乳突病毒所感染的细胞产生的蛋白，结合并抑制pRb，最终导致癌症。

The retinoblastoma protein (protein name abbreviated pRb; gene name abbreviated RB or RB1) is a tumor suppressor protein that is dysfunctional in several major cancers. One function of pRb is to prevent excessive cell growth by inhibiting cell cycle progression until a cell is ready to divide. When the cell is ready to divide, pRb is phosphorylated, becomes inactive and allows cell cycle progression. It is also a recruiter of several chromatin remodeling enzymes such as methylases and acetylases.