Washington State Route 510

State Route 510
A map of the area located between Tacoma and Chehalis showing SR 510, highlighted in red.
Route information
Auxiliary route of I‑5
Defined by RCW 47.17.685
Maintained by WSDOT
Length	13.10 mi (21.08 km)
Existed	1964 – present
Major junctions
West end	I‑5 in Lacey
East end	SR 507 in Yelm
Highway system
State highways in Washington Interstate US State Scenic Former PSH 1964 renumbering Former ← SR 509 SR 512 →

State Route 510 Alternate
Location	Yelm
Length	1.17 mi (1.88 km)
Existed	2010–present

State Route 510 (SR 510) is a 13.07-mile (21.03 km) long state highway in Thurston County, a subdivision of the US state of Washington. The highway extends southeast from an interchange with Interstate 5 (I-5) in Lacey to SR 507 in Yelm. SR 510 roughly parallels the Nisqually River, the border between Thurston and Pierce counties, between the Fort Lewis and Nisqually Indian Community area to Yelm.

The roadway was built by 1916 as a connector from Saint Clair Lake to the Northern Pacific Railway station in Yelm and was designated as Secondary State Highway 5I (SSH 5I) in 1937. The original route of SSH 5I ran from Tumwater east to Yelm, following the present-day Yelm Highway. In 1959, the highway was realigned to serve a new freeway, later I-5, in Lacey; SSH 5I was replaced in the 1964 highway renumbering by SR 510. The Yelm-Tenino Trail was built over the Northern Pacific line in 1993 and a bypass is being constructed around Yelm.