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 (formerly Central Link) in King County and Snohomish County, which travels for 33 miles (53 km) between Lynnwood, Seattle, and Seattle–Tacoma International Airport; the 2 Line in King County's Eastside region between Bellevue and Redmond; and the T Line (formerly Tacoma Link) 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 94,500 per weekday as of the third quarter of 2024, primarily on the 1 Line. Trains run at frequencies of 6 to 24 minutes.
The Link light rail system was originally conceived in the 1980s following several earlier proposals for a heavy rail system that were rejected by voters. Sound Transit was created in 1993 and placed a ballot measure to fund and build the system, which was passed on a second attempt in 1996. Tacoma Link began construction first in 2000 and opened on August 22, 2003, at a cost of $80 million. Central Link construction was delayed because of funding issues and routing disputes, but began in November 2003 and was completed on July 18, 2009, for $2.4 billion. Central Link trains initially ran from Downtown Seattle to Tukwila International Boulevard station before being extended south to the airport in December 2009, north to the University of Washington in March 2016, and further south to Angle Lake station in September 2016. An extension to Northgate station opened on October 2, 2021, and a further extension to Lynnwood Transit Center opened on August 30, 2024.
The first phase of the 2 Line opened on April 27, 2024, between South Bellevue and Redmond Technology stations. It is scheduled to be extended west to Seattle and east to Downtown Redmond by 2025. Sound Transit plans to expand the Link light rail network to 116 miles (187 km) and 83 stations by 2044, using funding approved by voters in 2008 and 2016 ballot measures. A suburban extension to Federal Way is scheduled to open in 2026 after construction delays. Later projects will expand the system to cover the metropolitan area from Everett to Tacoma, along with branches to Kirkland, Issaquah, and the Seattle neighborhoods of Ballard and West Seattle.