Antagonism may refer to:
The characteristic of an antagonist
Antagonism (chemistry), where the involvement of multiple agents reduces their overall effect
Drug antagonism, a drug that stops the action or effect of another substance, preventing a biological response
Receptor antagonism or pharmacological antagonism, the action of a drug that inhibits the function of an agonist at the level of a receptor
Antagonism (phytopathology), an effect that suppresses the activity of a plant pathogen
Reflexive antagonism of muscles
Intraspecific antagonism, disharmonious or antagonistic interaction between two individuals of the same species
