Forest Park, Urban forest park in the Tualatin Mountains, Portland, Oregon, United States

Forest Park is a public municipal park in the Tualatin Mountains west of downtown Portland, Oregon. It covers more than 5,100 acres of mostly second-growth forest, with Douglas-fir, western hemlock and western red cedar among the main trees. The park runs about 8 miles along the West Hills above the Willamette River, from West Burnside Street to the river's divide around Sauvie Island, and more than 80 miles of trails cross it.

In 1851 settlers cleared Douglas-fir on the slopes for housing, but landslides after heavy rain cancelled the plans and the land was donated to the city. In 1897 merchant Donald Macleay gave 43.7 hectares along Balch Creek for hospital patients' outdoor recreation. After the 1903 Olmsted Brothers report, parcels were assembled through donations, county transfers and tax foreclosures; the park was formally dedicated on 23 September 1948.

The park's name comes from its role as a forested reserve, and its trails are marked with blue mileage posts every quarter mile. The Wildwood Trail, the longest path, begins near the Oregon Zoo and runs about 30 miles to Northwest Newberry Road. The 40-Mile Loop, though named for 40 miles, actually extends about 150 miles through the Portland area.

The Wildwood Trail runs about 43 km inside the park, from trail marker 0 near the Oregon Zoo in Washington Park to marker 30 at Northwest Newberry Road, with blue mileage markers placed roughly every 400 m. Most paths are pedestrian-only, while some roads allow bicycles or horses. Leif Erikson Road, closed to motor vehicles, parallels the Wildwood Trail for about 18 km from Northwest Thurman Street to Northwest Germantown Road.

The largest tree in the park is a Douglas-fir near an abandoned public restroom along Balch Creek; it stands 74 metres tall with a trunk circumference of about 5.67 metres at its base. Douglas-firs here can live up to 750 years and reach roughly 73 metres.