A trial court or court of first instance is the court in which most civil or criminal cases begin. Not all cases are heard in trial courts; some cases may begin in inferior limited jurisdiction bodies such as the case of the jurisdiction of an administrative body that has been created by statute to make some kind of binding determination under the law and were simplified procedural practices may apply similar to arbitration.

In the trial court evidence is taken and determinations are made called findings of fact based on the evidence under the rules of evidence of the court following the applicable procedural law; the court also makes findings of law based upon the applicable law. Findings of fact are determined by the trier of fact (judge or jury) and the findings of law are always determined by the judge or judges. In most common law jurisdictions, the trial court often sits with a jury and one judge; though some cases may be "bench trials" — either by statute, custom, or by agreement of the parties — in which the judge makes both fact and law determinations.

A trial court is distinguished from an appellate court, which reviews cases that have already been heard in the trial court. In appellate review the record of the trial court must be certified by the clerk of the trial court and transmitted to the appellate body. Most appellate courts do not have the authority to hear testimony or take evidence, but must rely upon the record below. Most trial courts are courts of record. The trial court is the court where the record of the presentation of evidence is created and must be maintained or transmitted to the appellate court.

The United States district court is the sole trial court of general jurisdiction in the federal judicial system. State court systems refer to their trial courts by a variety of names, including "district court", "circuit court", "superior court", and (in New York) "Supreme court".