An interstate compact is an agreement between two or more U.S. states. The United States Constitution provides that states may not enter into such agreements without the consent of Congress. Frequently, these agreements create a new governmental agency which is responsible for administering or improving some shared resource such as a seaport or public transportation infrastructure. In some cases, a compact serves simply as a coordination mechanism between independent authorities in the member states. The lists below reflect this distinction.

Operating interstate agencies

• Bi-state Development Agency (Missouri and Illinois)
• Delaware River Port Authority (Pennsylvania and New Jersey)
• Delaware River Joint Toll Bridge Commission (Pennsylvania and New Jersey)
• Delaware River and Bay Authority (Delaware and New Jersey)
• Port Authority of New York and New Jersey (New Jersey and New York)
• Washington Metropolitan Area Transportation Authority (Maryland, Virginia, and Washington, D.C.)

Non-operating interstate compacts

• Northeast Dairy Compact (formerly set fluid milk prices the New England states)