Washington Park is a public park in Seattle, Washington, United States, most of which is taken up by the Washington Park Arboretum, a joint project of the University of Washington, the Seattle Parks and Recreation, and the nonprofit Arboretum Foundation. Washington Park also includes a playfield and the Seattle Japanese Garden in its southwest corner.

To the north is Union Bay; to the west are Montlake and Madison Valley; to the south is the Washington Park neighborhood; and to the east is the Broadmoor Golf Club.

Lake Washington Boulevard E. runs north and south through the park, parallel to the creek. A secondary road, for most of its length named Arboretum Drive E. and for a short northern stretch named E. Foster Island Road, runs along the Arboretum's eastern edge. E. Interlaken Boulevard and Boyer Avenue E. run northwest out of the park to Montlake and beyond. State Route 520 cuts through Foster Island and the Union Bay wetlands at the park's northern end, interchanging with Lake Washington Boulevard just outside the arboretum entrance. A footpath winds underneath the freeway overpasses and over boardwalks, along the Lake Washington ship canal, and into the gardens of the Arboretum.

The Arboretum is well known for Azalea Way in the springtime, a stretch of the park which offers a unique tapestry of azaleas of many colors. The area is a popular site for strolling and is utilized by photographers and artists. The manicured Azalea Way stands out in stark contrast with the Arboretum's wild and heavily canopied areas.

The land occupied by the Washington Park Arboretum has been developed and is owned by the city, but the Arboretum is operated primarily by the University of Washington.

Arboretum Creek is approximately 4,000 feet (1,200 m) long, entirely within the park. Its average channel width is 4 feet (1.2 m) and its average channel depth is 2 feet (0.61 m). The creek's source is a spring-fed stream in the Alder Creek Natural Area, three publicly owned properties on 26th Ave East between East Helen and Prospect streets. The stream feeds the koi pond in Washington Park's Japanese Garden, near the playfield at the park's southern end. It also receives runoff from Rhododendron Glen and the Woodland Garden, as well as sub-surface drainage from the neighboring course of the Broadmoor Golf Club. It empties into Lake Washington via Willow Bay, itself a minor arm of Union Bay, having passed through numerous culverts under Lake Washington Boulevard.