Acadia (French: Acadie) was a colony of New France in northeastern North America which included parts of what are now the Maritime provinces, the Gaspé Peninsula and Maine to the Kennebec River. During much of the 17th and early 18th centuries, Norridgewock on the Kennebec River and Castine at the end of the Penobscot River were the southernmost settlements of Acadia. The French government specified land bordering the Atlantic coast, roughly between the 40th and 46th parallels. It was eventually divided into British colonies. The population of Acadia included the various indigenous First Nations that comprised the Wabanaki Confederacy, the Acadian people and other French settlers.

The first capital of Acadia was established in 1605 as Port-Royal. A British force from Virginia attacked and burned down the town in 1613, but it was later rebuilt nearby, where it remained the longest-serving capital of French Acadia until the British siege of Port Royal in 1710. There were six colonial wars in a 74-year period in which British interests tried to capture Acadia, starting with King William's War in 1689. French troops from Quebec, Acadians, the Wabanaki Confederacy, and French priests continually raided New England settlements along the border in Maine during these wars. Acadia was conquered in 1710 during Queen Anne's War, while New Brunswick and much of Maine remained contested territory. Prince Edward Island (Île Saint-Jean) and Cape Breton (Île Royale) remained under French control, as agreed under Article XIII of the Treaty of Utrecht. The English took control of Maine by defeating the Wabanaki Confederacy and the French priests during Father Rale's War. During King George's War, France and New France made significant attempts to regain mainland Nova Scotia. The British took New Brunswick in Father Le Loutre's War, and they took Île Royale and Île Saint-Jean in 1758 following the French and Indian War.

The term Acadia today refers to regions of North America that are historically associated with the lands, descendants, or culture of the former region. It particularly refers to regions of The Maritimes with Acadian roots, language, and culture, primarily in New Brunswick, Nova Scotia, the Magdalen Islands, and Prince Edward Island, as well as in Maine. It can also refer to the Acadian diaspora in southern Louisiana, a region also referred to as Acadiana. In the abstract, Acadia refers to the existence of an Acadian culture in any of these regions. People living in Acadia are called Acadians which changed to Cajuns in Louisiana, the American pronunciation of Acadians, even though most Cajuns are not descendants of Acadians but French-Americans who lived in southern Louisiana in the US, a region which became known there as Acadiana in the latter part of the 20th century.