Engel v. Vitale, 370 U.S. 421, is a landmark 1962 United States Supreme Court case that determined school prayer, even when relatively non-denominational and voluntary, is unconstitutional.

The case was brought by the parents of several students who complained the prayer to "Almighty God" contradicted their religious beliefs, and was supported by various groups opposed to the school prayer. The prayer in question was:

Almighty God, we acknowledge our dependence upon Thee, and we beg Thy blessings upon us, our parents, our teachers and our country. Amen.

The plaintiffs argued that opening the school day with such a prayer (even if students are not required to recite it) violates the Establishment Clause of the First Amendment, which says, "Congress shall make no law respecting an establishment of religion". They further argued that this clause also applies to the states under the Fourteenth Amendment.

Justice Hugo Black, writing for the majority, pointed out that the prayer is a religious activity by the very nature of its being a prayer. The majority further ruled that prescribing such a religious activity for school children is inconsistent with the Establishment Clause. That is, the program was created by government officials to promote a religious belief, and therefore not permissible.

In response to the defendant's claims that: a) the prayer does not respect any specific established religion; and b) the prayer is voluntary, Black's opinion held that neither of these claims frees it from contradicting the Establishment Clause. The opinion held that the fact that it promotes a religion is sufficient to conclude it is in violation, even if that promotion is not coercive. Furthermore, the opinion held that the fact that the prayer is vaguely worded enough to not promote any particular religion is not a sufficient defense, as it does still promote a family of religions (those that recognize "Almighty God"), which is also a violation of the Establishment Clause.

See also: List of United States Supreme Court cases