A blue slip or blue-slipping is one of two different legislative procedures in the United States Congress.
- Blue slip (U.S. Senate) is the slip on which the senators from the state of residence of a federal judicial nominee gives an opinion on the nominee.
- Blue slip (U.S. House of Representatives) is the rejection slip given to tax and spending bills sent to it by the Senate that did not originate in the House in the first place, per the House's interpretation of the Origination Clause.