Glycoprotein V (platelet) (GP5) also known as CD42d (Cluster of Differentiation 42d), is a part of the Ib-V-IX system of surface glycoproteins that constitute the receptor for von Willebrand factor (VWF) and mediate the adhesion of platelets to injured vascular surfaces in the arterial circulation, a critical initiating event in hemostasis.

The main portion of the receptor is a heterodimer composed of 2 polypeptide chains, an alpha chain (GP1BA) and a beta chain (GP1BB), that are linked by disulfide bonds. The complete receptor complex includes noncovalent association of the alpha and beta subunits with platelet glycoprotein IX (GP9) and GP5. Mutations in GP1BA, GP1BB, and GP9 have been shown to cause Bernard-Soulier syndrome , a bleeding disorder.