The Main Street Tunnel, located in Welland, Ontario, Canada, is an underwater tunnel, carrying Niagara Road 27 and the unsigned designation of Highway 7146 under the Welland Canal.

The tunnel links Highway 406 on the west side of the canal, which travels north to St. Catharines to Highway 140 on the east side, which travels south to Port Colborne.

The tunnel provides four lanes for traffic, two in each direction, separated by a full-height concrete wall.

This price was split 50–50 between Transport Canada and the St. Lawrence Seaway Authority.

The tunnel opened with a parade featuring the Welland Police pipe band and various officials on the morning of May 20, 1972.