The Adirondack Park is a publicly protected area in northeast New York. It is the largest park and the largest state-level protected area in the contiguous United States, and the largest National Historic Landmark.

The park covers some 6.1 million acres (2.5×10^⁶ ha), a land area greater than Vermont, or than Yellowstone, Yosemite, Grand Canyon, Glacier, and Great Smoky Mountains National Parks combined. However, over half of the area is privately owned . Considering that fact, while acknowledging that Death Valley National Park encompasses over 3 million acres of entirely publicly owned land, Death Valley should be considered the largest protected land in the lower 48 .

Much of the land is directly controlled by the state's Forest Preserve, but more than half the land within the Adirondack Park is privately owned, including several villages and hamlets.

The Adirondack Park boundary, commonly referred to as the 'Blue Line,' contains the entire Adirondack Mountain range, as well as some surrounding areas, all within the state of New York. The park includes all of Hamilton and Essex counties, as well as considerable portions of Clinton, Franklin, Fulton, Herkimer, St. Lawrence, and Warren counties and small portions of Lewis, Oneida, Saratoga, and Washington counties as well. (The Clinton County towns of Altona and Dannemora, despite being entirely within the park boundary, are specifically excluded from the park by statute, due to the large prison facilities in both towns.)