An allegation (also called adduction) is a claim of a fact by a party in a pleading, which the party claims to be able to prove. Allegations remain assertions without proof, until they can be proved.

There are also marital allegations: marriage bonds and allegations exist for couples who applied to marry by licence. They do not exist for couples who married by banns. The marriage allegation was the document in which the couple alleged (or frequently just the groom alleged on behalf of both of them) that there were no impediments to the marriage.

Generally, in a civil complaint, a plaintiff alleges facts sufficient to establish all the elements of the claim and thus states a cause of action. The plaintiff must then carry the burden of proof and the burden of persuasion in order to succeed in the lawsuit.

A defendant can allege affirmative defenses in its answer to the complaint.

Other allegations are required in a pleading to establish the correct jurisdiction, personal jurisdiction and subject matter jurisdiction.