Matthias II was Duke of Lorraine from 1220 to his death. He was the son of Duke Frederick II and Agnes of Bar and succeeded his brother, Theobald I.
He immediately had to give away Nancy to his brother's widow, Gertrude of Dagsburg, who remarried to Theobald IV of Champagne, whose suzerainty Matthias had to recognise, due to the fruitless wars his brother had waged against an imperial coalition. Theobald had hoped to get his hands on the county of Metz, but failing that, he repudiated Gertrude. Gertrude had no children by a third marriage and Nancy reverted to the duchy on her death in 1225.
Matthias accompanied Emperor Frederick II on the Sixth Crusade in 1228 and into Italy in 1235. By this, he reinitiated the close alliance with the Holy Roman Emperors which his forefathers had had for over a century from the appointment of Adalbert until the war between his brother and Frederick, which had ruptured that long friendship.
Matthias faced several unruly barons, especially the Count of Lunéville, who had the discreet support of the Count of Bar. He was victorious and reattached Lunéville to the duchy in an exchange. However, peace was not achieved.