Udo was a ninth-century nobleman of East Francia, a son of Gebhard, Count of Lahngau, and older brother of Berengar I of Neustria. He and his brother were afforded their position in the March of Neustria both by kinship to Adalard the Seneschal and the favour of Charles the Bald.

With his brothers, Berengar and Waldo the Abbot, he took part in the 861 revolt of Carloman of Bavaria, possible his cousin-in-law, against Louis the German. The revolt was crushed and the three brothers fled with their relative Adalard to the court of the West Frankish king, Charles the Bald, who granted them wardship of the march against the Vikings while the march against the Bretons was granted to Robert the Strong.

Charles' patronage of the family provoked the jealousy of the Rorgonids, the most powerful family local to Neustria and then controlling the ducatus Cenomannicus (Maine). In 865, they allied with Saloman of Brittany and attacked the brothers. Charles, to attain peace, took the march back and gave it to Gauzfrid, a Rorgonid.