Oregon v. Mitchell, 400 U.S. 112 (1970) was a case decided by the United States Supreme Court.

Plantiff "Oregon" was the U.S. state of that name. Defendant "Mitchell" was John Mitchell in his role as United States Attorney General. Congress had passed an act requiring all states to register citizens between the ages of 18 and 21 as voters. Oregon did not desire to lower its voting age to 18, and filed suit on the grounds that the act was unconstitutional.

The Supreme Court found largely for Oregon, in that it found that while Congress could set requirements for voting in federal elections that it did not have the power to set the voting age for state elections.

Obviously, enforcement of this ruling would have proven to be problematic, as states not desiring to lower the voting age to 18 would then have to have provided special federal-election only ballots to citizens between 18 and 21 who desired to vote in federal elections, and would have required the maintenance of two sets of voting registries, one for those between 18 and 21 and another for those over 21.

This question became moot with the ratification of the Twenty-sixth Amendment the next year, which empowered Congress to legislate the lowering of the voting age to 18 for all elections in all states.