Oregon Route 339 (OR 339) is an Oregon state highway running from the Washington state line near Ferndale to Milton-Freewater.

It is 3.43 miles (5.52 km) long and runs north–south, entirely within Umatilla County.

OR 339 begins at an intersection with State Line Road approximately one and one half miles north of Ferndale, at the Washington state line, and heads south through Ferndale and Sunnyside.

Approximately one-half-mile south of Sunnyside, OR 339 intersects OR 332.

OR 339 ends at the Milton-Freewater northern city limit.