The University Link tunnel is a 3.15-mile (5.07 km) light rail tunnel in Seattle, Washington. The twin-bore tunnel carries Link light rail service on the University Link Extension of Central Link, running from the Downtown Seattle Transit Tunnel to University of Washington station via Capitol Hill station. The 21 ft-wide (6.4 m) tunnels are lined with precast gasketed concrete segments connected with steel bolts and was excavated using three tunnel-boring machines in 2011 and 2012. Light rail service began on March 19, 2016.

Link light rail is a light rail rapid transit system serving the Seattle metropolitan area in the U.S. state of Washington. It is managed by Sound Transit in partnership with local transit providers, and consists of three non-connected lines: the 1 Line in King County, which travels for 26 miles (42 km) between Seattle and Seattle–Tacoma International Airport; the 2 Line in King County's Eastside region between Bellevue and Redmond; and the T Line in Pierce County, which runs for 4 miles (6.4 km) between Downtown Tacoma and Tacoma Dome Station. In 2023, the system had a ridership of 23.9 million, or about 78,600 per weekday as of the fourth quarter of 2023, primarily on the 1 Line. Trains run at frequencies of 6 to 24 minutes.