Neustria was the western part of the Kingdom of the Franks during the Early Middle Ages, in contrast to the eastern Frankish sub-kingdom, Austrasia. It initially included land between the Loire and the Silva Carbonaria, in the north of present-day France, with Paris, Orléans, Tours, Soissons as its main cities.
The same term later referred to a smaller region between the Seine and the Loire rivers known as the regnum Neustriae, a constituent subkingdom of the Carolingian Empire and then West Francia. The Carolingian kings also created a March of Neustria which was a frontier duchy against the Bretons and Vikings that lasted until the Capetian monarchy in the late 10th century, when the term was eclipsed as a European political or geographical term.