The Cajuns (; French: les Cadjins or les Cadiens [le ka.dʒɛ]), also known as Louisiana Acadians (French: les Acadiens), are a Louisiana French ethnicity mainly found in the U.S. state of Louisiana.

While Cajuns are usually described as the descendants of the Acadian exiles who went to Louisiana over the course of Le Grand Dérangement, Louisianians frequently use Cajun as a broad cultural term (particularly when referencing Acadiana) without necessitating descent from the deported Acadians. Although the terms Cajun and Creole today are often portrayed as separate identities, Louisianians of Cajun descent have historically been known as Creoles. Cajuns make up a significant portion of south Louisiana's population and have had an enormous impact on the state's culture.

While Lower Louisiana had been settled by French colonists since the late 17th century, many Cajuns trace their roots to the influx of Acadian settlers after the Great Expulsion from their homeland during the French and British hostilities prior to the French and Indian War (1756 to 1763). The Acadia region to which many modern Cajuns trace their origin consisted largely of what are now Nova Scotia, New Brunswick, Prince Edward Island plus parts of eastern Quebec and northern Maine.

Since their establishment in Louisiana, the Cajuns have become famous for their French dialect, Louisiana French, and have developed a vibrant culture including folkways, music, and cuisine. Acadiana is heavily associated with them.