Loire-Atlantique (French pronunciation: [lwa.ʁat.lɑ̃.tik]; formerly Loire-Inférieure) is a department on the west coast of France named after the Loire River and the Atlantic Ocean.

Loire-Atlantique is one of the original 83 departments created during the French Revolution on March 4, 1790. Originally, it was named Loire-Inférieure, but its name was changed in 1957 to Loire-Atlantique.

The area is part of Brittany, and contains what many people still consider to be Brittany's capital, Nantes. There is a campaign to have it reintegrated in Brittany.

Loire-Atlantique is part of the current region of Pays-de-la-Loire and is surrounded by the department of Morbihan, Ille-et-Vilaine, Maine-et-Loire, and Vendée, with the Atlantic on the west.

Upper Brittany's indigenous language is Gallo, a romance language related to French. The number of Gallo language speakers has been in steady decline since the early 20th century. The language is neither official nor taught in primary or secondary education. The Breton language, a Celtic language, native to Lower Brittany, was historically spoken in the western area of Loire-Atlantique, and up to 1920 in Batz-sur-Mer. This area (Guérande, Le Croisic, and La Baule) has a rather Breton toponymy: for instance, Guérande originates from the Breton Gwenn Rann (white or pure place).