The Sumner Tunnel is a road tunnel in Boston, Massachusetts, United States. It carries traffic under Boston Harbor in one direction, from Logan International Airport and Route 1A in East Boston. The tunnel originally deposited traffic at the west side of the North End, but with the completion of the Big Dig, it was modified to have two exits. One exit connects to I-93 northbound and downtown Boston near Haymarket Station. The other exit connects to Storrow Drive and Nashua St., connecting Cambridge via Route 28. Traffic headed for I-93 southbound and the Massachusetts Turnpike (I-90) westbound is normally routed to the Ted Williams Tunnel.

Route 1A is a north–south state highway in Massachusetts, United States. It is an alternate route to U.S. 1 with three signed sections and two unsigned sections where the highway is concurrent with its parent. Due to the reconfiguration of tunnel interchanges brought on by the completion of the Big Dig, Route 1A is discontinuous in the downtown Boston area. Vehicles entering Downtown Boston via the Sumner Tunnel must take I-93 north to the exit for Government Center and make a U-turn to access the entrance ramp to I-93 south and vice versa.