In U.S. constitutional law, a facial challenge is a challenge to a statute in which the plaintiff alleges that the legislation is always unconstitutional, and therefore void. It is contrasted with an as-applied challenge, which alleges that a particular application of a statute is unconstitutional.

If a facial challenge is successful, a court will declare the statute in question facially invalid, which has the effect of striking it down entirely. This contrasts with a successful as-applied challenge, which will result in a court narrowing the circumstances in which the statute may constitutionally be applied without striking it down. In some cases—e.g., Gonzales v. Carhart or Crawford v. Marion County Election Board, a facial challenge has been rejected with either the court or concurring Justices intimating that the upheld statute might be vulnerable to an as-applied challenge.

In First Amendment cases, another type of facial challenge is enunciated in the overbreadth doctrine. If a statute reaches to include substantially protected conduct and speech in relation to the legitimate reach of the statute, then it is overbroad and thus void on its face.