In English law, oyer and terminer (; a partial translation of the Anglo-French oyer et terminer, which literally means "to hear and to determine") was one of the commissions by which a judge of assize sat. Apart from its Law French name, the commission was also known by the Law Latin name audiendo et terminando, and the Old English-derived term sac and soc.

By the commission of oyer and terminer the commissioners (in practice the judges of assize, though other persons were named with them in the commission) were commanded to make diligent inquiry into all treasons, felonies and misdemeanours whatever committed in the counties specified in the commission, and to hear and determine the same according to law. The inquiry was by means of the grand jury; after the grand jury had found the bills of indictment submitted to it, the commissioners proceeded to hear and determine by means of the petit jury. The words oyer and terminer were also used to denote the court that had jurisdiction to try offences within the limits to which the commission of oyer and terminer extended.