This is a list of megaprojects in the Seattle area. For this list, a megaproject follows the often cited definition of $1 billion (2017 dollars) or more.
| Name | Type | Status | Cost | Notes | |
|---|---|---|---|---|---|
| Sound Transit 3 | Transit | $54 billion[1] | Divided between several projects, to open between 2024 and 2041 | ||
| Vancouver B.C.–Seattle–Portland high-speed railway | Transit | Initiative of the Pacific Coast Collaborative between state and provincial governments | |||
| State Route 520 bridge replacement and corridor program | Road | $4.56 billion[2] | New bridge opened in April 2016, rest of corridor anticipated to be complete by 2029 | ||
| Alaskan Way Viaduct replacement tunnel | Road tunnel | $4.25 billion (2009 est.)[3] | |||
| Amazon headquarters, Seattle | Office buildings | $4 billion[4] | |||
| East Link Extension | Transit line | $3.7 billion[5] | Scheduled to open in 2023 | ||
| Lynnwood Link Extension | Transit line | $2.9 billion[6] | Scheduled to open in 2024 | ||
| Interstate 405 (Eastside) improvements | Road | [7] | 2003 Nickel and 2005 Transportation Partnership Account: $1.5 billion; 2015 Connecting Washington package: $1.3 billion | ||
| Central Link, Seattle and Tukwila | Transit line | $2.44 billion[8] | |||
| Spring District, Bellevue | Urban development | $2.3 billion[9] | Scheduled to open in phases from 2017 to 2026 | ||
| Puget Sound Gateway (SR 167 and SR 509) | Road | $1.989 billion[10] | |||
| Northgate Link tunnel | Transit tunnel | $1.9 billion[11] | |||
| Brightwater Tunnel | Sanitation infrastructure | $1.8 billion[12] | First billion-dollar tunnel in Seattle | ||
| University Link tunnel | Transit tunnel | $1.7 billion[13] | Completed $200 million under budget. Central Link light rail service began in 2016. | ||
| Interstate 5 HOV lanes in Tacoma and Fife | Road expansion | $1.6 billion[14] | Scheduled to be complete in 2022 | ||
| Yesler Terrace redevelopment | Urban development | $1.5 billion[15] | May increase to $1.7 billion | ||
| Lincoln Square expansion, Bellevue | Urban development | $1.2 billion[16] | |||
| Seattle–Tacoma International Airport third runway | Airport infrastructure | $1.1 billion | Does not include $200 million in soundproofing for schools | ||
| Seattle seawall replacement | Shoreline infrastructure | $1.07 billion (2014 estimate)[17] | |||
| Mount Baker Tunnel | Road tunnel | [18] | Earliest billion-dollar project on this list | ||
| Point Ruston | Urban development | $1 billion[19] | |||
| Snoqualmie Ridge | Master-planned community | $1 billion[20] | Made suburb of Snoqualmie the fastest growing city in Washington (2010) | ||
| Hewitt Avenue Trestle replacement (U.S. Route 2, Everett) | Road bridge | ||||
| Puget Sound salmon recovery–culvert replacement | Stream restoration | $3.7 billion | Began in 1991, expanded by June 2018 U.S. Supreme ruling in favor of tribal fisheries rights. Projected to continue through 2030. |
Notable Washington state megaprojects outside the immediate Seattle area include the following: