New Jersey v. T. L. O., 469 U.S. 325 (1985), is a landmark decision by the Supreme Court of the United States which established the standards by which a public school official can search a student in a school environment without a search warrant, and to what extent.

The case centered around a student at Piscataway High School in Middlesex County, New Jersey, known then only by her initials T. L. O., who was searched for contraband after she was caught smoking in a school bathroom. She was sent to the principal's office, where the vice principal searched her purse and found marijuana, drug paraphernalia, and documentation of drug sales. She was expelled from the school and charged by police for the paraphernalia found in the search, but fought the charges on the basis that the search of her purse violated the Fourth Amendment's prohibition against unreasonable search and seizure.

The New Jersey Superior Court affirmed the constitutionality of the search, but the Supreme Court of New Jersey reversed, holding that the search of her purse was unreasonable. On appeal to the U.S. Supreme Court, the Court held that the Fourth Amendment applies to searches conducted by school officials in a school setting. However, school officials do not need to have probable cause nor obtain a warrant before searching a student. Instead, in order for a search to be justified, school officials must have "reasonable suspicion" that the student has violated either the law or school rules. In a 6–3 decision delivered by Justice Byron White, the Court ruled that the school's search of T. L. O.'s purse was constitutional, setting a new precedent for school searches and student privacy.