Oregon Route 99W is a state-numbered route in Oregon, United States, that runs from OR 99 and OR 99E in Junction City north to I-5 in southwestern Portland. Some signage continues it north to US 26 near downtown, but most signage agrees with the Oregon Department of Transportation's (ODOT) description, ending it at I-5. OR 99W is known by ODOT as the Pacific Highway West No. 1W ; that highway continues north through downtown to the Pacific Highway No. 1 (I-5) in northern Portland, as well as south on OR 99 to the Pacific Highway (I-5) in Eugene.

U.S. Route 99 (US 99) was a main north–south United States Numbered Highway on the West Coast of the United States until 1964, running from Calexico, California, on the Mexican border to Blaine, Washington, on the Canadian border. It was assigned in 1926 and existed until it was replaced for the most part by Interstate 5. Known also as the "Golden State Highway" and "The Main Street of California", US 99 was important throughout much of the 1930s as a route for Dust Bowl immigrant farm workers to traverse the state. Large portions are now California State Route 99 (SR 99), Oregon's Routes 99, 99W, and 99E, and Washington's SR 99. The highway in Washington connected to British Columbia Highway 99, whose number was derived from that of US 99, at the Canada–US border.