Bothell (/ˈbɒθəl/) is a city in King and Snohomish counties in the U.S. state of Washington. It is part of the Seattle metropolitan area, situated near the northeast end of Lake Washington in the Eastside region. It had a population of 48,161 residents as of the 2020 census.

The city lies along the Sammamish River, the historic home of the indigenous Sammamish people, and is adjacent to Kenmore and Woodinville. It was established in 1870 and platted by David Bothell and his family in 1888, shortly before the arrival of railroads in the area. The town was incorporated in 1909 and originally relied on logging and farming; in the mid-20th century, it became a bedroom community for workers commuting to Seattle and later other Eastside cities. Interstate 405 connects the city to other areas of the Eastside and functions as a bypass of Seattle.

Bothell's modern economy is centered around biotechnology and high-tech companies that have facilities that were developed in the late 20th century along North Creek and in the Canyon Park neighborhood, which was annexed by the city in 1992. The annexation also expanded the city limits into Snohomish County. The University of Washington Bothell was established in 1990 and opened its permanent shared campus with Cascadia College in 2000. Bothell redeveloped its downtown in the 2010s and 2020s and has seen an increase in residential density and its population as a result.

The Sammamish River valley from Lake Washington to Issaquah Creek was first inhabited by the indigenous Sammamish people (Lushootseed: sc̓ababš), a Coast Salish group with an estimated population of 80 to 200 around 1850. The Sammamish had a major winter village, ƛ̕ax̌ʷadis, at the mouth of the Sammamish River, between what is now Bothell and Kenmore. Although the Sammamish resisted removal efforts by settlers, they were eventually removed to Fort Kitsap following the 1855–1856 Puget Sound War. Some Sammamish continued to live in the area and worked as laborers and farmers, but the village of ƛ̕ax̌ʷadis was later destroyed.

The first Homestead Act claims to modern-day Bothell were filed in 1870 by Columbus S. Greenleaf and George R. Wilson, an English immigrant, on adjoining plots of land. The area along the lower Sammamish River, then named Squak Slough, was mostly marshlands and had not been surveyed at the time of Wilson's arrival; Greenleaf filed for his claim in June 1870 on land that Wilson had originally sought. Eight families settled in the area in the next six years and were followed by Canadian businessman George Brackett, who began commercial logging in 1877 on 80 acres (32 ha) on the modern-day site of Wayne Golf Course. Brackett also established Brackett's Landing, which had a sawmill and steamboat dock served by traffic from Seattle and Issaquah.

In 1884, Brackett sold 80 acres (32 ha) of his timberland to David Bothell, a settler and American Civil War veteran from Pennsylvania. Bothell and his two sons built a home and shingle mill on the property the following year and later opened a boarding house with his wife. The boarding house was destroyed by a fire and replaced by the Bothell Hotel at another location, where the townsite was platted on April 25, 1888. The settlement was named for the Bothell family by the first postmaster Gerhard Ericksen, who had bought the boarding house property. At the time, the area had two hotels, several lumber mills, and a school. Bothell originally shared schools with Woodinville until a separate school district was established in 1885; the first classes at Bothell's schoolhouse were held in March 1886. The school district was merged with North Creek in 1897 and ten years later, a dedicated school building was constructed to accommodate the growing student population.

The Seattle, Lake Shore and Eastern Railway was constructed along the Sammamish River to connect Seattle to the transcontinental Northern Pacific Railway as well as coal from mines near Issaquah. The tracks reached Bothell in November 1888 and a boxcar was placed at Brackett's Landing to serve as a temporary station; it was moved east to Bothell in 1890 and later replaced by a depot building. A county road was built between Bothell and neighboring Woodinville to the east. Several logging railroads were also constructed in the Bothell area, stretching as far north as modern-day Canyon Park, to transport logs to local mills; one included a trestle bridge across the Sammamish River. Bothell grew rapidly following the railroad's opening; by the end of the 1880s, it had telegraph service, a general store, a butcher, and a drugstore with a practicing doctor. Many of the new residents were Scandinavian or Eastern European immigrants, along with emigrants from the Midwest. The first churches in the area were established by these immigrants in the mid-1880s. Two of the local mills were destroyed in fires in 1893 and 1894 and were later replaced with a larger facility that produced 80,000 shingles per day.

Bothell was incorporated as a fourth-class town on April 14, 1909, eight days after a narrow 79–70 vote in favor. George Bothell, one of the sons of David Bothell and a former state legislator, was elected as the first mayor. At the time, the town had a population of 599 residents, a bank, four general stores, and three saloons. A dozen buildings on Main Street were destroyed or damaged by a fire on April 11, 1911, including the Ericksen general store where the town's records had been kept. A fire department was established in 1913 and new building regulations were enacted by the town government in response to the fire. The Pacific Highway was completed through the town in August 1912, connecting to Everett and Seattle. A 4-mile (6.4 km) section west of Bothell was the first to be paved in brick; it was inaugurated on May 29, 1913, by Washington governor Ernest Lister.