The Apostle Islands National Lakeshore is a U.S. national lakeshore consisting of 21 islands (the Apostle Islands) and shoreline encompassing 69,540 acres (28,140 ha) in northern Wisconsin, on the shore of Lake Superior. It is known for its collection of historic lighthouses, sandstone sea caves, a few old-growth remnant forests, and natural animal habitats. Of its area, 42,308 acres (17,121 ha) is land and 27,232 acres (11,020 ha) is water, extending one-quarter mile from the 155 miles (249 km) of shoreline.

The national lakeshore is managed by the National Park Service and headquartered in Bayfield, Wisconsin, on Lake Superior. Madeline Island, with commercial establishments of the town of La Pointe, is the only one of the Apostle Islands not included in the national lakeshore, although a portion of the island is protected as Big Bay State Park. Apostle Islands National Lakeshore is featured on the America the Beautiful quarters series.

Beginning in the west, going north around the outer islands, then west, then east, ending with the southernmost island, the Apostle Islands included in the national lakeshore are:

Historical evidence suggests that another island formerly existed alongside Eagle Island. It was known as Steamboat Island, although this name was apparently also used for Eagle Island itself, in which case Steamboat Island was called "Little Steamboat Island". Multiple sources dating from August 1901 document the disappearance of the island around that time, due to unknown natural forces.

The Apostle Islands are a result of the glaciers that once covered North America. "Geologically they are originally part of the main land at the edge of the great rift or fault which formed the depression to which the waters of Lake Superior collected." When the glaciers melted, waves from the waters of Lake Superior caused erosion that formed the islands. The islands are composed of mostly red sandstone because of the glacial shift.^{[clarification needed]}

It is widely assumed that Native Americans were the first to inhabit the island. "There is some evidence that they were seen and possibly visited sometime in the fourteenth century by Indians who were making their way to Isle Royale near the north shore of the land in search of copper." In the 17th century, the islands were visited by Étienne Brûlé, a French explorer who, like many French Canadians, was trying to discover a new way to the East Indies. "Historians believe that the Jesuits named the islands the Apostle Islands according to their practice of giving holy names to new places." It is said that fur traders were the first explorers to settle in the area, building a village from the money they brought in.

Previously used for logging, farming, and mining during the early 20th century, the islands are returning to a primitive state; evidence of human habitation is still present, albeit mostly obscured by the regenerating forests. The islands' coastlines possess varied geology, where precambrian sandstone has eroded into sea caves, and the resulting sand has formed sandspits, cuspate forelands, tombolos, barrier spits, and beaches.

United States Senator Gaylord Nelson sponsored the federal legislation that established the Apostle Islands National Lakeshore. Public Law 91-424 was signed by President Richard M. Nixon on September 26, 1970. It included 20 islands, a 12-mile (19 km) strip of the mainland, and approximately 1/4 mile of Lake Superior jurisdiction adjacent to each land unit.