Hagerstown is a city in Washington County, Maryland, United States, and its county seat. The population was 43,527 at the 2020 census. Hagerstown ranks as Maryland's sixth-most populous incorporated city and is the most populous city in the Maryland Panhandle.

Hagerstown anchors the Hagerstown metropolitan area extending into West Virginia. It makes up the northwesternmost portion of the Washington–Baltimore combined statistical area in the heart of the Great Appalachian Valley. The population of the metropolitan area in 2020 was 293,844. Greater Hagerstown was the fastest-growing metropolitan area in the state of Maryland and among the fastest growing in the United States, as of 2009.

Hagerstown has a distinct topography, formed by stone ridges running from northeast to southwest through the center of town. Geography accordingly bounds its neighborhoods. These ridges consist of upper Stonehenge Limestone. Many of the older buildings were built from this stone, which is easily quarried and dressed onsite. It whitens in weathering and the edgewise conglomerate and wavy laminae become distinctly visible, giving an appearance unique to the Cumberland Valley as seen in the architecture of St. John's Episcopal Church.

Despite its semi-rural Western Maryland setting, Hagerstown is a center of transit and commerce. Interstates 81 and 70, CSX, Norfolk Southern, and the Winchester and Western railroads, as well as Hagerstown Regional Airport form an extensive transportation network for the city. Hagerstown is also the chief commercial and industrial hub for a greater tri-state area that includes much of Western Maryland as well as significant portions of South Central Pennsylvania and the Martinsburg Panhandle Area. Hagerstown has often been referred to as, and is nicknamed, the Hub City.

In 1739, Jonathan Hager, a German immigrant from Pennsylvania and a volunteer Captain of Scouts, purchased 200 acres (81 ha) of land in the Great Appalachian Valley between the Blue Ridge and Allegheny Mountains in Maryland and called it Hager's Fancy. In 1762, Hager officially founded the town of Elizabethtown which he named after his wife, Elizabeth Kershner. Fourteen years later, Jonathan Hager became known as the "Father of Washington County" after his efforts helped Hagerstown become the county seat of newly created Washington County, which Hager also helped create from neighboring Frederick County. The City Council changed the community's name to Hager's-Town in 1813 because the name had gained popular usage, and in the following year, the Maryland State Legislature officially endorsed the changing of the town's name.

In 1794, government forces arrested 150 citizens during a draft riot which was staged by protesters in response to the Whiskey Rebellion.

Hagerstown's strategic location at the border between the North and the South made the city a primary staging area and supply center for four major campaigns during the Civil War. In 1861, General Robert Patterson's troops used Hagerstown as a base to attack Virginia troops in the Shenandoah Valley. In the Maryland Campaign of 1862, General James Longstreet's command occupied the town while en route to the Battle of South Mountain and Antietam. In 1863, the city was the site of several military incursions and engagements as Gen. Robert E. Lee's army invaded and retreated in the Gettysburg Campaign. In 1864, Hagerstown was invaded by the Confederate army under Lt. Gen. Jubal Early. On Wednesday, July 6, Early sent 1,500 cavalry, commanded by Brig. Gen. John McCausland, into Hagerstown. The Confederates levied a ransom of $20,000 and a large amount of clothing, in retribution for U.S. destruction of farms, feed and cattle in the Shenandoah Valley. This is in contrast to neighboring Chambersburg, Pennsylvania, which McCausland razed on July 30 when the borough failed to supply the requested ransom of $500,000 in U.S. currency, or $100,000 in gold.

Following the war, in 1872 Maryland and Virginia cooperated to re-inter Confederate dead from their impromptu graves to cemeteries in Hagerstown, Frederick and Shepherdstown, West Virginia. Roughly 60% however, remained unidentified. In 1877, 15 years after the Battle of Antietam, also known as the Battle of Sharpsburg, approximately 2,800 Confederate dead from that battle and also from the battles on South Mountain were re-interred in Washington Confederate Cemetery, within Rose Hill Cemetery in Hagerstown.