Olney, a census-designated place and an unincorporated area of Montgomery County, Maryland, U.S., is located in the north central part of the county, twenty miles (32 km) north of Washington, D.C. As generally defined, Olney had a total population of 33,844 in the 2010 U.S. Census.
Originally known as Mechanicsville, the village which became Olney was established in 1800. The area was mostly farmland, but it soon began attracting artisans. Early residents Sarah Brooke and Dr. Charles Farquhar were devotees of the English poet William Cowper, and named their home after the poet's hometown. The area was in turn named for their home, which still stands and is known as the Olney House. The Brooke family held the largest tracts of land in Olney, whose central village was at the intersection of the Rockville to Baltimore road, and the one which connected Washington with Westminster, Maryland, to the north. The Quaker community in Sandy Spring thrived just to Olney's east. The Sandy Spring Museum is a historical museum featuring educational programs and displays. St. John's Episcopal Church was established in 1842 and survives to this day.