State Route 525 (SR 525) is a 30.68-mile-long (49.37 km) state highway located in Snohomish and Island counties in the western region of the U.S. state of Washington. SR 525 begins at an interchange with Interstate 5 (I-5) and I-405 in Lynnwood and travels north to SR 99 as a four-lane controlled-access freeway. From Lynnwood, the highway serves Mukilteo and becomes the terminus of SR 526 before taking its ferry route to Clinton on Whidbey Island.