is a rule that a final judgment on the merits by a court of competent jurisdiction is conclusive of the rights of the parties or their privies in all subsequent suits on all points and matters determined in the former suit. It is a ground for dismissal. – Taganas vs. Emuslan

Elements of Res Judicata

(1) the former judgment or order must be final; (2) the judgment or order must be on the merits; (3) it must have been rendered by a court having jurisdiction over the subject matter and the parties; (4) there must be, between the first and the second action, identity of parties, of subject matter and cause of action. – Allied Banking vs. CA

Notes

It is one of the only four grounds in which motions to dismiss are allowed, together, they are:

1. The court has no jurisdiction over the subject matter of the claim
2. Litis Pendentia
3. Res Judicata
4. Prescription