Hanover is a borough in York County, Pennsylvania, United States. The population was 16,429 at the 2020 census. Located 19 miles (31 km) southwest of York and 54 miles (87 km) north-northwest of Baltimore, Maryland, the town is situated in a productive agricultural region. It is named after the German city of Hanover and is a principal city of the York–Hanover metropolitan area.

Hanover was the site of the final encounter between the Union and Confederate armies before they fought against each other in the Battle of Gettysburg during the American Civil War. Hanover has since become known as the "Snack Food Capital of the World" due to the establishment of multiple food manufacturing businesses there during the 20th century. Notable companies based in the borough include Utz Brands and Snyder's of Hanover.

In 1727, John Digges, an Irish nobleman of Prince George's County, Maryland, obtained a grant of 10,000 acres (40 km²) of land where Hanover is now located from Charles Calvert, 5th Baron Baltimore. The area was called Digges Choice, and in 1730, a group of Catholics started the settlement that became known as the Conewego Settlement. Settlers from both Maryland and Pennsylvania began moving into the area in the 1730s. At this time, Maryland and Pennsylvania did not agree on the northern border of Maryland and the southern border of Pennsylvania, and the area that is now Hanover was in the disputed area claimed by both states. This led to numerous disputes about property ownership from the 1730s until 1760. The dispute was settled when Maryland and Pennsylvania hired British expert surveyors Charles Mason and Jeremiah Dixon to survey what became known as the Mason–Dixon Line. This line was surveyed between 1763 and 1767, and put an end to decades of disputes over rights and ownership.

In 1745, a Scot-Irishman named Richard McAllister (father of Matthew McAllister) purchased the tract of land upon which the original town of Hanover was built. McAllister was a Presbyterian who had recently migrated from the Cumberland Valley. Hanover at that time was covered with a dense forest of hickory, walnut, and oak trees. McAllister erected a log house at what is now the corner of Baltimore and Middle streets, and opened a store and tavern. In 1763, McAllister divided his farm into lots and founded the town of Hanover. German settlers nicknamed the settlement "Hickory Town" after the thick groves of hickory trees that grew in the area. The name Hanover was suggested by Michael Tanner, who was one of the commissioners who laid out York County in 1749 and owned large tracts of land southeast of the town. Tanner's choice of the name came from the fact that he was a native of Hanover, Germany. The town's founders, who wanted to please the German settlers, agreed to the name. Hanover was also sometimes referred to as "McAllister's Town" in its early years.

Thomas Jefferson spent the night of April 12, 1776 at the Sign of the Horse, an inn, owned by Caspar Reinecker on Frederick Street. Records indicate that Jefferson paid "Rhenegher" 11 shillings, 6 pence for dinner and lodging. He was on his way from Monticello to Philadelphia to attend the first meeting of the Continental Congress, where on June 10 he would begin to draft the Declaration of Independence. At the time, Hanover was located at the crossing of two well-traveled roads, one from the port of Baltimore to points north and west and the other between Philadelphia and the Valley of Virginia. When Jefferson returned from Philadelphia to Monticello, he again dined and spent the night of September 5 at Reinecker's inn.

At the start of the Revolutionary War, Hanover consisted of about 500 homes, most of which were built out of logs. After the war, the population increased steadily until the War of 1812. At the time of the advance of the British on Baltimore in 1814, Hanover and vicinity furnished two companies of infantry commanded by Captain Frederick Metzgar and John Bair. These two companies left Hanover on foot Sunday morning, August 28, 1814, and reached the city of Baltimore at 9 A.M., Tuesday. September 11, where they were marched to North Point, spending that night on their arms, and next day, the memorable September 12, 1814, they took part in the engagement with the British, who retreated soon after. The Hanover Companies together with other companies from York County, returned home after two weeks' service, not being needed longer.

After the War of 1812, the town experienced only minor growth until 1852, when construction of the Hanover Branch Railroad to Hanover Junction was completed. In 1858 the Gettysburg Railroad opened a railroad link westward to Gettysburg. The Hanover and York Railroad completed a rail line to York in 1876.

During the American Civil War, the Battle of Hanover was fought on June 30, 1863. Union cavalry under Judson Kilpatrick encountered Confederate cavalry under J.E.B. Stuart and a sharp fight ensued in the town and in farm fields to the south, particularly along Frederick Street. The final encounter between Union and Confederate forces prior to the Battle of Gettysburg, this inconclusive engagement delayed the Confederate cavalry on their way to the Battle of Gettysburg. Three days before the battle, another detachment of Virginia cavalry had briefly occupied Hanover, "collecting" supplies and horses from local citizens.