Nouvelle-Aquitaine (French pronunciation: [nuvɛl akitɛn] ^ⓘ) is the largest administrative region in France by area, located in the west and southwest of Metropolitan France. It was created in 2014 from the merger of Aquitaine, Limousin, and Poitou-Charentes in a territorial reform. The region covers 84,035.7 km² (32,446.4 sq mi), representing more than 1⁄7 of Metropolitan France, and had a population of 6,033,952 in 2020. The new region was formally established on 1 January 2016, following the regional elections in December 2015.

The region is larger in area than any other French region, including overseas regions such as French Guiana, and has a landmass that is slightly greater than Austria. Bordeaux is the prefecture and largest city; its metropolitan area has about 850,000 inhabitants. The region has 25 major urban areas, among which the most important after Bordeaux are Bayonne (288,000 inhabitants), Limoges (283,000), Poitiers (255,000), Pau (241,000) and La Rochelle (206,000), as well as eleven major clusters.

Nouvelle-Aquitaine has five universities (Bordeaux, La Rochelle, Limoges, Poitiers and Pau) and several Grandes Écoles. It has three of the four historic resorts on the French Atlantic coast: Arcachon, Biarritz and Royan, as well as ski resorts in the Pyrenees, including Gourette.

Its economy includes agriculture, viticulture (notably the vineyards of Bordeaux and Cognac), tourism, aerospace manufacturing, the digital sector, design, chemical and pharmaceutical production, financial service in Niort, and industrial ceramics in Limoges. The new region includes major parts of Southern France ("Midi de la France"), influenced by Basque, Occitan, Poitevin and Saintongeais cultures. Historically, it is the "indirect successor" to medieval Aquitaine; much of the region was part of the former Duchy of Aquitaine.

The region's interim name Aquitaine-Limousin-Poitou-Charentes was a hyphenated placename, known as ALPC, created by hyphenating the merged regions' names – Aquitaine, Limousin and Poitou-Charentes – in alphabetical order.

In June 2016, a working group headed by historian Anne-Marie Cocula [fr], a former vice-president of Aquitaine, proposed the name "Nouvelle Aquitaine", meaning "New Aquitaine". The decision came after the popular favourite, "Aquitaine", faced resistance by regional politicians from Limousin and Poitou-Charentes. The other popular favourite, "Grande Aquitaine", was rejected for its connotation with a feeling of superiority. Alain Rousset, president of the region, concurred with the working group's conclusion, reaffirming that he considered the acronym "ALPC" no choice at all. For those deploring the loss of "Limousin" and "Poitou-Charentes", he noted that the predecessor region of Aquitaine subsumed the identities of the Périgord or the Pays Basque, which did not disappear during its 40 years of operation.

On 27 June 2016, just a few days ahead of 1 July deadline, the Regional Council almost unanimously adopted Nouvelle-Aquitaine as the region's permanent name. France's Conseil d'État approved Nouvelle-Aquitaine as the new name of the region on 28 September 2016, effective two days later.

At 84,061 square kilometres, Nouvelle-Aquitaine is larger than French Guiana, which makes it the largest region of metropolitan and overseas France.