The Chesapeake Bay Bridge (commonly known as the Bay Bridge) is a major dual-span bridge in the U.S. state of Maryland. Spanning the Chesapeake Bay, it connects the state's rural Eastern Shore region with the more urban Western Shore. The original span opened in 1952 and, at the time, with a length of 4.3 miles (6.9 km), it was the world's longest continuous over-water steel structure. The parallel span was added in 1973. The bridge is officially named the William Preston Lane, Jr. Memorial Bridge after William Preston Lane, Jr. who, as governor of Maryland, initiated its construction.

The bridge is part of U.S. Routes 50 and 301, and serves as a vital link in both routes. As part of U.S. Route 50, it connects the Baltimore-Washington Metropolitan Area with tourist destinations such as Ocean City, Maryland, Delaware's ocean resorts, Assateague Island, and Chincoteague, Virginia. As part of U.S. Route 301, it serves as part of an alternate route for Interstate 95 travelers between northern Delaware and the Washington, D.C. area. Because of this linkage, the bridge is heavily traveled and has become known as a point of traffic congestion, particularly during peak hours and summer months.