The Monitor–Merrimac Memorial Bridge–Tunnel (MMMBT) is the 4.6 mi Hampton Roads crossing for Interstate 664 (I-664) in the southeastern portion of Virginia in the United States. It is a four-lane bridge–tunnel composed of bridges, trestles, artificial islands, and tunnels under a portion of the Hampton Roads harbor where the mouths of the James, Nansemond, and Elizabeth rivers come together.