The predecessor to Neustria was a Roman rump state, the
Kingdom of Soissons. In 486 its ruler,
Syagrius, lost the struggle for power with
Clovis I, the Frankish king, in the
Franco Roman War. He was beaten in the
Battle of Soissons and the domain was thereafter under the control of the Franks. Constant re-divisions of territories by Clovis's descendants resulted in many rivalries that, for more than two hundred years, kept Neustria in almost constant warfare with Austrasia, the eastern portion of the Frankish
Kingdom. Despite the wars, Neustria and Austrasia re-united briefly on several occasions. The first was under
Clotaire I during his reign from 558 to 562. The struggle for power continued with Queen
Fredegund of Neustria, the widow of King
Chilperic I (reigned 566–584) and the mother of the new king
Clotaire II (reigned 584–628), unleashing a bitter war. After his mother's death and burial in
Saint Denis Basilica near Paris in 597,
Clotaire II continued the struggle against
Queen Brunhilda, and finally triumphed in 613 when Brunhilda's followers betrayed the old queen into his hands. Clotaire had Brunhilda put to the
rack and stretched for three days, then chained between four horses and eventually ripped limb from limb. Clotaire now ruled a united realm, but only for a short time as he made his son
Dagobert I king of Austrasia. Dagobert's accession in Neustria resulted in another temporary unification. In Austrasia the
Pippinid mayor Grimoald the Elder attempted a
coup by forcing the Austrasian king Siegebert III to adopt his son Childebert who succeeded as "Childebert the Adopted". Grimoald and his son Childebert were arrested by Neustrian forces and executed in Paris.
Clovis II, after this execution, again reunited the Austrasian kingdom with Neustria, although temporarily. During or soon after the reign of Clovis's son
Chlothar III, the dynasty of Neustria, like that of Austrasia before it, ceded authority to its own mayor of the palace. In 678, Neustria, under Mayor
Ebroin, subdued the Austrasians for the last time. Ebroin was murdered in 680. In 687,
Pippin of Herstal, mayor of the palace of the King of Austrasia, defeated the Neustrians at
Tertry. Thus he guaranteed the predominance of Austrasia, characterized by its territorial aristocracy, over Neustria. Neustria's mayor
Berchar was assassinated shortly afterwards and following a marriage alliance () between Pippin's son
Drogo and Berchar's widow
Anstrud of Champagne, Pippin secured his position as mayor of the Neustrian palace. Pippin's descendants, the
Carolingians, continued to rule the two realms as mayors. With
Pope Stephen II's blessing, after 751 the Carolingian
Pippin the Short formally deposed the Merovingians and took control of the empire, he and his descendants ruling as kings. Neustria, Austrasia, and
Burgundy then became united under one authority and, although it would split once again into various eastern and western divisions, the names "Neustria" and "Austrasia" gradually fell out of use. ==Carolingian subkingdom==