State Route 106 (SR 106) is a Washington state highway in Mason County, extending 20.09 miles (32.33 km) from U.S. Route 101 (US 101) in Skokomish to SR 3 south of Belfair.

PSH 21 became SR 106 in 1964 and since, the Washington State Department of Transportation has arranged and completed minor projects to improve the roadway.

From the intersection, the road travels southeast to bridge Skobob Creek and curve north along the Skokomish River and Annas Bay to the community of Union.

After passing Union, the highway continues along the southern shoreline of Hood Canal past Twanoh State Park to intersect SR 3 south of Belfair.

[11] Recently, the Washington State Department of Transportation (WSDOT) has arranged and completed some minor construction projects along the SR 106 corridor.