Reginar I, Count of Hainaut

Reginar I Longneck (c. 850 – 915) was the Duke of Lorraine from 910 until his death. He stands at the head of the clan of Reginarids, an important Lotharingian noble family and was the grandson of the emperor Lothair I.

He was the son of Gilbert, Count of the Maasgau, and a daughter of Lothair I of whom the name is not known (Hiltrude, Bertha, Irmgard, and Gisela are good candidates).

He succeeded his father in the Maasgau and was the lay abbot of Echternach between 897 and 915, of Maastricht from before May 898, and of Stablo and Malmedy between 900 and 902.

He was the Count of Mons and Count of Liège when in 870 he and Franco, Bishop of Liège, led an army against the Vikings in Walacria. He, as Duke of Hesbaye and Hainault, and Radbold led a Frisian army against the forces of Rollo a little later, but were forced back to his fortresses.

In the 877 Capitulary of Quierzy, he appears alongside his father as one of the regents of the kingdom during Charles the Bald's absence on campaign in Italy. A Reginar appears at the Siege of Paris in 886, but this may be an uncle or nephew. The name "Reginar" or "Reginhar" (French: Régnier or Rainier) was commonplace in his family.