French Cerdagne

French Cerdagne (Catalan: Alta Cerdanya, ) is the northern half of Cerdanya, which came under French control as a result of the Treaty of the Pyrenees in 1659, while the southern half remained in Spain (as part of Catalonia). Catalonians often refer to French Cerdagne as Upper Cerdanya (Catalan: Alta Cerdanya). It is the only French territory in the Iberian Peninsula, as it is in the south side of the Pyrenees range between Spain and France. For example, the Segre river, which goes west and then south to meet the Ebro, has its source in the French Cerdagne.

French Cerdagne has no special status inside France, simply forming an area within the department of Pyrénées-Orientales, unlike the Spanish part of Cerdanya, which is officially a Catalan comarca called simply Cerdanya. In France, the French area is referred to as either Cerdagne française (i.e. "French Cerdagne"), Haute Cerdagne (i.e. "Upper Cerdagne") or just Cerdagne.

French Cerdagne has a land area of 539.67 km² (208.37 sq. miles). Its 1999 population was 12,035, resulting in a density of only 22 people per km² (58 per sq. mile).

French Cerdagne has the most cloud-free days in France, and was therefore chosen as the place to build:

• the solar furnace of Odeillo (Catalan: Odelló) (official site), used for high-temperature scientific experiments;
• the Thémis experimental solar power plant (operated by EDF from 1983 to 1986); it is now decommissioned as a power plant, but is being used as a Cerenkov telescope for the detection of Gamma rays