Mill Creek is a city in Snohomish County, Washington, United States. It is located between the cities of Everett and Lynnwood, approximately 20 miles (32 km) northeast of Seattle. The city has a population of 20,926 as of the 2020 census. The city lies along State Route 527 and North Creek, a tributary of the Sammamish River, on the east side of Interstate 5.

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The city is one of the wealthiest suburbs in the Seattle metropolitan area and was originally a planned community conceived in the 1970s. The planned development was centered around a country club and golf course, with other development occurring nearby in later phases. It was incorporated as a city in 1983, shortly after the completion of the first phase of development, and underwent major population growth due to continued suburban development and annexation of nearby areas. The city's downtown area is centered around the Mill Creek Town Center, a mixed-use lifestyle center and retail complex that opened in 2004.