The Minisink or (more recently) Minisink Valley is a loosely defined geographic region of the Upper Delaware River valley in northwestern New Jersey (Sussex and Warren counties), northeastern Pennsylvania (Pike and Monroe counties) and New York (Orange and Sullivan counties).

The name was derived by Dutch colonists from the Munsee name for the area, as bands of their people took names after geographic places which they inhabited as territory throughout the mid-Atlantic area. Originally inhabited by Munsee, the northern branch of the Lenape or Delaware Indians, the area's first European settlers arrived in the late seventeenth and early eighteenth centuries and were Dutch and French Huguenot families from colonial New York's Hudson River Valley. The term "Minisink" is not used often today. It is preserved because of its historical relevance concerning the early European settlement of the region during the American colonial period and as an artifact of the early "first contact" between Native Americans and early European explorers, traders and missionaries in the seventeenth century.

Much of the historical Minisink region has been incorporated into the Delaware Water Gap National Recreation Area after defeat of a controversial dam project proposed to be built by U.S. Army Corps of Engineers on the Delaware River near Tocks Island.

The name Minisink comes from the Munsee dialect of Lenape, a group of similar Algonquian dialects that were spoken by the various groups of Lenape, or Delaware Indians who inhabited the region before European colonization. Minisink means "at the island" from the Algonquin root word minis, meaning island.^{[citation needed]}

During the colonial period, the Minisink was also an area of significant skirmishes and raids between British and French-allied forces in the French and Indian War (the North American front of the Seven Years' War). In response to attacks by larger forces of Delaware, Benjamin Franklin ordered the construction of a series of forts along the Pennsylvanian side of the Delaware River. These forts included Fort Hyndshaw, Fort Dupuy, Fort Norris, and Fort Hamilton, among others.

Earlier historians posited that Minisink meant "people of the stony country" or "where the stones are gathered together." However, Smithsonian linguist Ives Goddard states that any of the attempts to derive either Minisink or Munsee from words meaning "stone" or "mountain," as proposed by these writers (including Lenape scholar Daniel G. Brinton), are incorrect.

The Minisink has never been known as a region with distinct, set boundaries. It generally has been conceived as the valley of the Delaware River going northward from the Delaware Water Gap and including the valley of the Neversink River (a tributary entering the Delaware near Port Jervis, New York). According to Vosburgh, "The 'Minisink county' consists of the valley of the Neversink west of the Shawangunk Mountains, and the Delaware valley, as far as the Delaware Water Gap." Some sources imply that it was confined to the width of valley of the Delaware and its surrounding hillsides.

Other sources define the region as an area extending for 20–30 miles to the east and west of the river. This latter definition would include parts or all of the Kittatinny Valley to the east of Kittatinny Mountain in New Jersey, and westward deep into northeastern Pennsylvania. East of the Shawangunk ridge, in New York are the Town of Greenville and the Town of Minisink, both often included as part of the Minisink region. Their residents attend Minisink Valley Central School District.