Res judicata is the generic term for a group of related concepts concerning the conclusive effects given final judgments. Within this general doctrine there are two principal categories: (1) claim preclusion—also known as res judicata; and (2) issue preclusion—also known as collateral estoppel.

These legal doctrines generally preclude litigants from relitigating claims and issues that were previously litigated to a final resolution or judgment.

In Alaska, as in other jurisdictions, res judicata and collateral estoppel are legal doctrines that prevent parties from relitigating matters that have already been resolved by a final judgment. Res judicata, or claim preclusion, bars a party from bringing a lawsuit on a claim that has been previously litigated and decided upon. This means that once a court has issued a final judgment on the merits of a case, the same parties cannot dispute the same claim in another lawsuit. Collateral estoppel, or issue preclusion, prevents the re-litigation of factual or legal issues that were necessarily decided in a previous lawsuit and are essential to the judgment. Even if the subsequent lawsuit is based on a different claim, parties cannot challenge an issue that has already been settled in court. These doctrines are meant to ensure the finality of legal decisions, conserve judicial resources, and protect parties from the burden of multiple lawsuits on the same matter. Alaska state statutes and case law align with these principles, providing guidance on their application in the state's legal system.