Sammamish (/səˈmæmɪʃ/ sə-MAM-ish) is a city in King County, Washington, United States. The population was 67,455 at the 2020 census. Located on a plateau, the city is bordered by Lake Sammamish to the west and the Snoqualmie Valley to the east. Sammamish is situated 20 miles east of Seattle, is a member of the Eastside, and is a part of the Seattle metropolitan area. Incorporated in 1999, Sammamish is an affluent community and has been ranked as one of the wealthiest cities in Washington.

Sammamish is a Snoqualmie name formed from the words "squax" (Sammamish Lake) and "abs", a suffix used to describe people of a specific area. The name is roughly translated to "people of Lake Sammamish" in the Snoqualmie language.

Lake Sammamish and the adjacent plateau has been Duwamish, Suquamish, Snoqualmie, Sammamish, and Snohomish territory since the last Pleistocene glaciation, before contact with European people. They lived in longhouse villages in seven places on and near the coast of Sammamish Lake. Two of them were in present-day Sammamish.

The Sammamish Plateau was part of unincorporated King County for most of its recorded history. The first settlers arrived in the 1870s and established a trio of resorts by the 1930s. The plateau remained a mostly rural area until suburban homes, shopping centers, and schools were built in the 1970s and 1980s. However, from approximately 1900 through the Great Depression, there was a tiny hamlet in Inglewood community (at today's Weber Point) of approximately 50 people who called the area "Sammamish", and later, in the 1960s, there was a suburban community and school at what is now Sunny Hills. A vote in 1991 to join neighboring Issaquah failed, as did a vote on incorporation the following year. A renewed movement to become a city, born of frustration with development policies set by the county government, met with voter approval in 1998. Sammamish was officially incorporated on August 31, 1999. The city annexed Klahanie on January 1, 2016.

The city government approved plans in 2008 to develop a denser town center with mixed use zoning and taller buildings. The first two residential buildings and several commercial developments were completed over the following decade, but plans for the largest phase stalled into the 2020s. Construction began in 2024 on 38 townhomes in the phase, which is planned to be followed by more townhomes, 600 market rate apartments, and commercial space.

According to the United States Census Bureau, the city has a total area of 24.04 square miles (62.26 km2), of which 20.43 square miles (52.91 km2) are land and 3.61 square miles (9.35 km2) are water.

The city is situated on the shores and hilly terrain east of Lake Sammamish. It is bordered to the south by Issaquah, to the northwest by Redmond, and to the west across Lake Sammamish by Bellevue. Beaver Lake and Pine Lake are the two biggest lakes in Sammamish. Yellow Lake is a major lake in Klahanie.

Sammamish is in and near the Issaquah Alps, a westward extension of the Cascade foothills.

The city has a warm-summer Mediterranean climate (Köppen: Csb), or oceanic (Köppen: Cfb) if the 30 millimetres (1.2 in) isohyet is used. Due to the rain shadow effect of the Olympic Mountains to the west, summers are much drier here than on the immediate west coast of Washington.

Winters are cool and wet; the wettest months are November, December, and January, when the area is directly affected by the Aleutian Low, and summers are warm and dry; the driest months are July and August. Snowfall is rare; subfreezing temperatures usually occur with a high-pressure system, which brings clear skies. Extremes range from −8 Â°F (−22 Â°C) in February 1950, to 113 Â°F (45 Â°C) in June 2021.

Sammamish is in hardiness zone 8b, with small southwestern pockets as well as the immediate Lake Sammamish coast falling into type 9a.

Sammamish is predicted to warm by 3-12 F (2-7 C) before 2100 regardless of future emissions, and around 2.5 F during the next few decades due to climate change. Warming by any significant amount will cause Sammamish to have reduced snowfall, hotter and drier summers, and more warm-season extreme weather events.

Sammamish's climate change action plan includes, but is not limited to, tree replacement, voluntary planting, protecting threatened species, protecting native fish such as Chinook salmon and the streams, lakes and ponds they live in, floodplain management, wetland protection, emission reduction, light/noise pollution reduction, toxin (pesticide) control, and many other measures.

As of the 2023 American Community Survey, there are 21,792 estimated households in Sammamish with an average of 2.98 persons per household. The city has a median household income of $238,750 and the per capita income was $103,748. Approximately 2.9% of the city's population lives at or below the poverty line. Sammamish has an estimated 66.7% employment rate, with 83.4% of the population holding a bachelor's degree or higher and 97.8% holding a high school diploma.

The U.S. Census Bureau estimated that the median household income in Sammamish was $239,000 in 2022, placing it first among U.S. cities with a population greater than 65,000.

The top five reported ancestries (people were allowed to report up to two ancestries, thus the figures will generally add to more than 100%) were English (56.3%), Spanish (3.4%), Indo-European (14.6%), Asian and Pacific Islander (24.4%), and Other (1.2%).

The median age in the city was 41.3 years.

In 2007, CNN Money ranked Sammamish as the 11th Best Place to Live in the United States, and subsequently ranked it as #12 in 2009 and #15 in 2011. Sammamish was also ranked the 9th Best Place to Live by Money.com in 2018.

As of the 2020 census, there were 67,455 people, 21,895 households, and 18,861 families residing in the city. The population density was 3,302.9 inhabitants per square mile (1,275.3/km2). There were 22,544 housing units at an average density of 1,103.9 per square mile (426.2/km2). The racial makeup of the city was 52.61% White, 1.28% African American, 0.21% Native American, 35.82% Asian, 0.10% Pacific Islander, 1.44% from some other races and 8.54% from two or more races. Hispanic or Latino people of any race were 5.36% of the population. 29.4% of residents were under the age of 18, 6.1% were under 5 years of age, and 51.1% were 65 and older. The gender makeup of the city was 51.1% female.

As of the 2010 census, there were 45,780 people, 15,154 households, and 12,918 families residing in the city. The population density was 2,512.2 inhabitants per square mile (970.0/km2). There were 15,736 housing units at an average density of 863.7 per square mile (333.5/km2). The racial makeup of the city was 74.72% White, 0.96% African American, 0.28% Native American, 19.34% Asian, 0.10% Pacific Islander, 0.86% from some other races and 3.74% from two or more races. Hispanic or Latino people of any race were 3.94% of the population.

There were 15,154 households, of which 52.9% had children under the age of 18 living with them, 76.9% were married couples living together, 5.6% had a female householder with no husband present, 2.7% had a male householder with no wife present, and 14.8% were non-families. 11.4% of all households were made up of individuals, and 2.1% had someone living alone who was 65 years of age or older. The average household size was 3.01 and the average family size was 3.28.

The median age in the city was 37.7 years. 32.2% of residents were under the age of 18; 4.9% were between the ages of 18 and 24; 27.9% were from 25 to 44; 29.4% were from 45 to 64; and 5.7% were 65 years of age or older. The gender makeup of the city was 50.1% male and 49.9% female.

As of the 2000 census, there were 34,104 people, 11,131 households, and 9,650 families living in the city. The population density was 1,888.9 inhabitants per square mile (729.3/km2). There were 11,599 housing units at an average density of 642.4 per square mile (248.0/km2). The racial makeup of the city was 87.82% White, 0.85% African American, 0.29% Native American, 7.89% Asian, 0.09% Pacific Islander, 0.60% from some other races and 2.46% from two or more races. Hispanic or Latino people of any race were 2.50% of the population.

There were 11,131 households, out of which 53.3% had children under the age of 18 living with them, 79.5% were married couples living together, 5.3% had a female householder with no husband present, and 13.3% were non-families. 9.4% of all households were made up of individuals, and 1.5% had someone living alone who was 65 years of age or older. The average household size was 3.06 and the average family size was 3.29.

In the city the population was spread out, with 33.4% under the age of 18, 4.8% from 18 to 24, 33.2% from 25 to 44, 24.6% from 45 to 64, and 4.0% who were 65 years of age or older. The median age was 35 years. For every 100 females, there were 101.7 males. For every 100 females age 18 and over, there were 98.5 males.

The median income for a household in the city was $101,592, and the median income for a family was $104,356. Males had a median income of $76,688 versus $47,164 for females. The per capita income for the city was $42,971. About 2.0% of the population and 1.6% of families were below the poverty line, including 1.7% of those under age 18 and 3.2% of those age 65 or over.

Sammamish has ten parks (Beaver Lake Park, Big Rock Park North, Big Rock Park, East Sammamish Park, Ebright Creek Park, Evans Creek Preserve, NE Sammamish Park, Pine Lake Park, Sammamish Commons, Sammamish Landing). Soaring Eagle Regional Park and Duthie Hill Park abut the city and are on the plateau. East Lake Sammamish Trail runs along the eastern side of Lake Sammamish and connects to a regional trail system, like the Sammamish River Trail to the north, and the Issaquah-Preston Trail to the south.

East Sammamish Park in the northwest of the city came with it in 1999.

The Sammamish City Council is elected by the community. Of the seven council members, two members are elected as Mayor and Deputy Mayor. Council meetings are held at City Hall, part of the Sammamish Commons, which is also the site of Sammamish Library, a branch of the King County Library System.

Sammamish does not have its own post office; the closest one is in Redmond. Eastside Fire and Rescue is contracted to provide fire services. Sammamish contracts with the King County Sheriff's Office for police services. Deputies assigned to Sammamish wear city uniforms and drive patrol cars marked with the city logo.

Sammamish's public school system is primarily served by two school districts.

North Sammamish is served by Lake Washington School District, and has two high schools (Eastlake, Tesla STEM), two middle schools (Inglewood, Renaissance School of Art and Reasoning), and five elementary schools (Elizabeth Blackwell, Rachel Carson, Christa McAuliffe, Margaret Mead, Samantha Smith).

South Sammamish is served by Issaquah School District, and has two high schools (Issaquah, Skyline), three middle schools (Beaver Lake, Pacific Cascade, Pine Lake), and seven elementary schools (Cascade Ridge, Cedar Trails, Challenger, Creekside, Discovery, Endeavour, Sunny Hills).

A very small portion to the east is in the Snoqualmie Valley School District.

Eastside Catholic School is a private school in the city.

Central Washington University is a public university that opened a Sammamish location on September 20, 2017.

Sammamish is served by three major north–south roads: East Lake Sammamish Parkway, 228th Avenue, and 244th Avenue. They connect to State Route 202 to the north, providing access to Redmond, and Interstate 90 to the south in Issaquah. A regional freeway, Interstate 605, has been proposed several times since the 1960s to run through Sammamish, but has not been built.

Bus service is provided by King County Metro routes 218, 269, and Sound Transit Express route 554 to Redmond, Issaquah, and Downtown Seattle. South Sammamish Park and Ride is the city's transit center with 265 parking stalls. Metro began running dial-a-ride buses to the Sammamish Plateau in 1993, and it later extended commuter services in the early 2000s.