State Court of Appeals Justice Christine Quinn-Brintnall will retire in January.
Quinn-Brintnall, who is being treated for melanoma, notified Gov. Jay Inslee via letter that she well step down effective Jan. 2, according to the Administrative Office of the Courts.
She is in her third term as an appellate judge and serves Division II, which hears appeals from 13 counties in Southwest Washington and the Olympic Peninsula, including Pierce and Thurston counties.
"It has been an honor to serve on this court, and the people of the state of Washington for the past 13 years," Quinn-Brintnall said in a statement. "While I am disappointed that I will not be able to finish my third term, I am confident that the governor will appoint a replacement who will serve the people of Washington well."
A replacement has not yet been named.