John Peter Zenger (October 26, 1697 – July 28, 1746) was a German-born American printer, publisher, editor and journalist in New York City.

He owned the second newspaper in the city, 'The New York Weekly Journal'. He printed another man's document that criticized William Cosby, Governor of New York, who had him arrested on a charge of seditious libel. Zenger claimed in his "apology" for missing an issue, that even though he was in jail without supplies, he could still publish by speaking through a hole in the door with the help of his wife and servants. It is unclear just how seriously Zenger personally took the material published in the Weekly Journal. It was almost certainly financed by one of the opposition factions in New York politics, possibly by James Alexander, who along with William Smith was disbarred for objecting to the two-man court that Cosby hand-picked. Zenger was most likely a convenient target to use in an attempt to end criticism. His defense attorney, Andrew Hamilton, was from Philadelphia, and won a case most local attorneys were confident would be unwinnable, and over which prior attorneys had been disbarred. His success resulted in the addition of the expression "Philadelphia lawyer" to the language with its original denotation of competence.

A notable aspect of the case is that Hamilton challenged the legality of the crimes for which his client was being prosecuted. It was one of the first times in American history in which a lawyer challenged the laws rather than the innocence of his clients. The jurors were stunned and didn't know how to, or even if they were allowed to, address whether the law itself was "legal." See also Jury nullification.