Nördlingen (German: [ˈnœʁtlɪŋən] ^ⓘ; Alemannic German: Nearle or Nerle) is a town in the Donau-Ries district, in Swabia, Bavaria, Germany, with a population of approximately 20,674. It is located approximately 115 km (71 mi) east of Stuttgart, and 145 km (90 mi) northwest of Munich. It was built in an impact crater 15 million years old and 25 km (16 mi) in diameter—the Nördlinger Ries—of a meteorite which hit with an estimated speed of 70,000 km/h, and left the area riddled with an estimated 72,000 tons of micro-diamonds.

Nördlingen was first mentioned in recorded history in 898. The town was the location of two battles during the Thirty Years' War, which took place between 1618 and 1648. Today it is one of very few towns in Germany that still have completely intact city walls—joining the ranks of Rothenburg ob der Tauber, Dinkelsbühl and Berching, all of them in Bavaria.

Another attraction in the town is Saint George's Church's 90-metre (300 ft) steeple, called "Daniel," which is made of a suevite impact breccia that contains shocked quartz. Other notable buildings are the town hall (which dates to the 13th century), St. Salvator church and the Spital, a former medieval hospital. The Ries crater museum is located in the well-preserved medieval tanners' quarter.

The city is home to several other museums, such as the Bavarian Railway Museum, the Nördlingen city museum (Stadtmuseum), the city wall museum (Stadtmauermuseum) and Augenblick museum. The latter has panoramas, magic lanterns, silent films, barrel organs, pianolas, music boxes, and gramophones.

Finds in the Ofnet Caves near the city show that the site of present-day Nördlingen was already inhabited in the late Palaeolithic. In the Large Ofnet, in 1908 archaeologist R. R. Schmidt found two dish-shaped pits in which human skulls were lying "like eggs in flat baskets". In the larger pit were 27 skulls and in the other there were 6 skulls. The skulls were arranged concentrically with their faces turned towards the setting sun. They were all covered with a thick layer of red ochre. The skulls have been dated to the 7th millennium BC. In the area around Nördlingen, additional sites dating to almost all of the subsequent prehistoric epochs have been discovered. Particularly important was an area on the eastern edge of the district Baldingen, where settlements have been found belonging to the Neolithic Linear Pottery culture, the Bronze Age Urnfield culture, and the Celtic Iron Age Hallstatt and La Tène cultures.

The area which includes present-day Nördlingen was part of the Roman province of Raetia, but little research has been conducted on the city's Roman period. A Roman villa has been excavated in the district of Holheim, and can be visited today. Another villa with an adjoining burial ground has been identified in the Baldingen district. A settlement (vicus), built in 85 C.E., occupied the southern part of the city until 259–260 C.E., when it was destroyed during the conquest of what is now southern Germany by the Germanic-speaking Alemanni tribes. The Roman settlement may have been the one known as Septemiacum, which is supposed to have been built between 80–300 C.E., although it is possible that this particular settlement was actually located at a different site such as Oberdorf, leaving the name of the settlement at Nördlingen uncertain.

The Alemannic people occupied the Nördlingen area during the 6th and 7th centuries, during which time the region was gradually Christianised under the Merovingian dynasty, and several burial grounds from this period have been discovered. The name "Nordilinga" is first found in documents of the Carolingian royal court dating from 898, and the city today celebrates this as the date of its "foundation". Under the rule of the Bishops of Regensburg, Nördlingen grew into an important market town.

In 1215, Nördlingen was granted city rights by Emperor Frederick II and became imperial city of the Holy Roman Empire. In that year, the first city wall was built, the footprint of which is still visible today. In a document dating to 1219, the Nördlinger Pfingstmesse ("Nördlingen Pentecost fair") was first mentioned, an event which continues as a folk festival in the city to the present day. Thanks to Nördlingen's location at the crossroads of two major trade routes (Frankfurt / Würzburg-Augsburg and Nuremberg-Ulm), it became an important trading centre for grain, livestock, textiles, furs, and metal goods. Besides Frankfurt am Main, Nördlingen was one of the most important long-distance trade fairs in the region.