Forest Grove is a city in Washington County, Oregon, United States, 25 miles (40 km) west of Portland, within the Tualatin Valley. Originally a small farm town, it is now primarily a commuter town in the Portland metro area ^{[citation needed]}. Settled in the 1840s, the town was platted in 1850, then incorporated in 1872, making it the first city in Washington County.^{[citation needed]}

The population was 26,225 at the 2020 census, an increase of 8% over 2010 figure (21,083).

Pacific University is located here. Old College Hall on campus, and nine other sites in the city, are listed on the National Register of Historic Places.

Prior to the 1840s when Euro-Americans settled the area, the Atfalati band of the Kalapuya Native American tribe lived on the Tualatin Plains in what is now Forest Grove. In 1841, Alvin T. and Abigail Smith were among the earliest to use the Oregon Trail and settled on what was first known as West Tualatin Plain. They overwintered with Henry Harmon Spalding, arriving in what is now Forest Grove in the fall. Intending to be missionaries, they found little potential as most of the natives had succumbed to European diseases. Smith served as the community's first postmaster beginning on February 1, 1850, and his log cabin served as the post office.

According to Oregon Geographic Names, the name Forest Grove was selected on January 10, 1851, at a meeting of the trustees of Tualatin Academy (later known as Pacific University). Resident and school trustee J. Quinn Thornton suggested the name, which he also had used for the name of his homestead. The name referred to a grove of oak trees that still stand on what is now the campus of the university. Previous post offices in the area were called Tuality Plains and Tualatin, with Forest Grove adopted on December 31, 1858. The city was platted in 1850.

In 1860, the population reached 430, but declined to 396 in 1870. Forest Grove was incorporated by the state in 1872, the first in the county. In 1880, the now Chemawa Indian School opened in the city to forcibly assimilate Native American children, but moved to Salem in 1884. The city started the Fire Department in 1894. The population reached nearly 1,300 in 1900.

In November 1908, the Oregon Electric Railway (OE) began serving the city, and in January 1914, competitor Southern Pacific (SP) followed suit, opening its own line, separate from OE's. Both railroads provided freight and passenger service, SP's passenger service being known as the Red Electric. A company called the Forest Grove Transportation Company operated local streetcar service that linked downtown to Carnation, Oregon, where the Oregon & California Railroad built its depot, but the service lasted only from 1906 to 1911. The Red Electric passenger service to Forest Grove ended in 1929 and Oregon Electric's ceased in 1932.

In February 2016, a high-pitched, hissing noise called the Forest Grove Sound was heard by several residents of the town.