Map - Montgomery County, Maryland (Montgomery County)

Montgomery County is the most populous county in the 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 and largest municipality is Rockville, although the census-designated place of Germantown is the most populous place within the county. Montgomery County, which adjoins Washington, D.C., is part of the Washington–Arlington–Alexandria, DC–VA–MD–WV metropolitan statistical area, which in turn forms part of the Baltimore–Washington combined statistical area. Most of the county's residents live in unincorporated locales, of which the most urban are Silver Spring and Bethesda, although the incorporated cities of Rockville and Gaithersburg are also large population centers, as are many smaller but significant places.

The average household income in Montgomery County is among the highest in the United States. It has the highest percentage (29.2%) of residents over 25 years of age who hold post-graduate degrees. Like other inner-suburban Washington, D.C. counties, Montgomery County contains many major U.S. government offices, scientific research and learning centers, and business campuses.

The Maryland state legislature named Montgomery County after Richard Montgomery; the county was created from lands that had at one point or another been part of Frederick County. On September 6, 1776, Thomas Sprigg Wootton from Rockville, Maryland, introduced legislation, while serving at the Maryland Constitutional Convention, to create lower Frederick County as Montgomery County. The name, Montgomery County, along with the founding of Washington County, Maryland, after George Washington, was the first time in American history that counties and provinces in the thirteen colonies were not named after British referents. The name use of Montgomery and Washington County were seen as further defiance to Great Britain during the American Revolutionary War. The county's nickname of "MoCo" is derived from "Montgomery County".

The county's motto, adopted in 1976, is "Gardez Bien", a phrase meaning "Watch Well". The county's motto is also the motto of its namesake's family.