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 Ohio, res judicata, or claim preclusion, prevents a party from relitigating a claim that has already been litigated and resulted in a final judgment. This doctrine ensures that a party cannot bring an action after it has been decided upon in a court of law, provided that the judgment was on the merits, the parties in both cases are the same or in privity, and the cause of action in the subsequent lawsuit was or could have been raised in the first lawsuit. Issue preclusion, also known as collateral estoppel, bars the relitigation of specific issues that were already litigated and essential to the final judgment in a previous lawsuit, even if the second lawsuit involves a different claim. Both doctrines are meant to promote judicial efficiency, uphold the integrity of court judgments, and protect parties from the burden of multiple lawsuits on the same matter. Ohio courts apply these principles in accordance with state statutes and case law precedent to determine the preclusive effect of prior judgments.