glycoprotein IIb/IIIa, also gpIIb/IIIa, is an integrin found on platelets. It is a receptor for fibrinogen and aids in platelet activation. The complex is formed via calcium-dependent association of gpIIb and gpIIIa, a required step in normal platelet aggregation and endothelial adherence.Platelet activation by ADP leads to a conformational change in in platelet gpIIb/IIIa receptors that induces binding to fibrinogen.

Genetic variation in glycoprotein IIb/IIIa (GPIIb/IIIa) as a determinant of the responses to an oral GPIIb/IIIa antagonist in patients with unstable coronary syndromes. Defects in glycoprotein IIb/IIIa cause Glanzmann's thrombasthenia. Autoantibodies against IIb/IIIa can be produced in immune thrombocytopenic purpura.Glycoprotein IIb/IIIa inhibitors can be used to prevent blood clots in an effort to decrease the risk of heart attack or stroke.