Gaithersburg is a city in Montgomery County, Maryland, United States. At the time of the 2020 census, Gaithersburg had a population of 69,657, making it the ninth-most populous community in the state. Gaithersburg is located to the northwest of Washington, D.C., and is considered a suburb and a primary city within the Washington metropolitan area. Gaithersburg was incorporated as a town in 1878 and as a city in 1968.

Montgomery County is the most populous county in the U.S. state of Maryland. As of the 2020 census, the county's population was 1,062,061, increasing by 9.3% from 2010. The county seat is Rockville and Germantown is the most populous place in the county. The county is adjoined to Washington, D.C., the nation's capital, and is part of the Washington metropolitan area and the Washington–Baltimore combined statistical area. Most of the county's residents live in Silver Spring, Bethesda, Germantown, and the incorporated cities of Rockville and Gaithersburg.