Gelderland (/ˈɡɛldərlənd/ GHEL-dər-lənd, Dutch: [ˈɣɛldərlɑnt] ^ⓘ), also known as Guelders (/ˈɡɛldərz/ GHEL-dərz) in English, is a province of the Netherlands, located in the centre-east of the country. With a total area of 5,136 km² (1,983 sq mi) of which 176 km² (68 sq mi) is water, it is the largest province of the Netherlands by land area, and second by total area. Gelderland shares borders with six other provinces (Flevoland, Limburg, North Brabant, Overijssel, South Holland and Utrecht) and the German state of North Rhine-Westphalia.

The capital is Arnhem (pop. 159,265); however, Nijmegen (pop. 176,731) and Apeldoorn (pop. 162,445) are both larger municipalities. Other major regional centres in Gelderland are Ede, Doetinchem, Zutphen, Harderwijk, Tiel, Wageningen, Zevenaar, and Winterswijk. Gelderland had a population of about 2,134,000 as of January 2023. It contains the Netherlands's largest forest region (the Veluwe), the Rhine and other major rivers, and a significant amount of orchards in the south (Betuwe).

Historically, the province dates from states of the Holy Roman Empire and takes its name from the nearby German city of Geldern. According to the Wichard saga, the Lords of Pont fought and killed a dragon in 878 AD, and named the town they founded after the death-rattle of the dragon: "Gelre!"

The County of Guelders arose out of the Frankish pagus Hamaland in the 11th century around castles near Roermond and Geldern. The counts of Gelre acquired the Betuwe and Veluwe regions and, through marriage, the County of Zutphen. Thus the counts of Guelders laid the foundation for a territorial power that, through control of the Rhine, Waal, Meuse and IJssel rivers, was to play an important role in the later Middle Ages. The geographical position of their territory dictated the external policy of the counts during the following centuries; they were committed to the interests of the Holy Roman Empire and to expansion south and west.

Further enlarged by the acquisition of the imperial city of Nijmegen in the 13th century, the countship was raised to a duchy in 1339 by the Holy Roman Emperor Louis IV. After 1379, the duchy was ruled from Jülich and by the counts of Egmond and Cleves. The duchy resisted Burgundian domination, but William, Duke of Jülich-Cleves-Berg was forced to cede it to Charles V in 1543, after which it formed part of the Burgundian-Habsburg hereditary lands.

The duchy revolted with the rest of the Netherlands against Philip II of Spain and joined the Union of Utrecht (1579). After the deposition of Philip II, its sovereignty was vested in the States of Gelderland, and the princes of Orange were stadtholders. In 1672, the province was temporarily occupied by Louis XIV and, in 1713, the southeastern part, including the ducal capital of Geldern, fell to Prussia. Part of the Batavian Republic (1795–1806), of Louis Bonaparte's Kingdom of Holland (1806–10), and of the French Empire (1810–13), Gelderland became a province of the Kingdom of the Netherlands in 1815.

During the Second World War, the area saw heavy fighting between Allied Paratroopers, British XXX Corps and the German II SS Panzer Corps, at the Battle of Arnhem.

Gelderland can roughly be divided into four geographical regions: the Veluwe in the north, the Rivierenland including the Betuwe in the southwest, the Achterhoek (literally meaning the "back corner") or Graafschap (which originally means earldom or county) in the east and the city-region of Arnhem and Nijmegen in the centre-south.