竞争性拮抗剂（英语：Competitive antagonist）是一种受体拮抗剂键结到受体后但并不活化受体。拮抗剂会跟促效剂(agonist)竞争同受体上的结合位点(binding sites)。强效的拮抗剂会将促效剂从结合位点取代出来，使受体的活化减低。

竞争性拮抗剂的存在将使促效作用的剂量-反应曲线(dose-response curve)向右横移。竞争性拮抗剂的Schild plot之斜率为1，且X、Y的截巨跟拮抗剂的解离常数(dissociation constant)相等。

竞争性拮抗剂可以是可逆性受体拮抗剂或者是不可逆性受体拮抗剂。

A competitive antagonist is a receptor antagonist that binds to a receptor but does not activate the receptor. The antagonist will compete with available agonist for receptor binding sites on the same receptor. Sufficient antagonist will displace the agonist from the binding sites, resulting in a lower frequency of receptor activation.