Venetia was a Byzantine ducatus, and part of the Exarchate of Ravenna, until it was conquered by the Lombards. The coastal parts of Venetia remained Byzantine, and was the origin of later Republic of Venice.
The account of the election of the first three doges of Venice (Pauluccio, Marcello and Orso), from the anonymous “Chronicon Altinate”.
The first doges, from the “Chronica per extensum descripta” (1340s) by Andrea Dandolo.
The name Venice is from the ancient tribe of the Veneti, whose lands became a Roman province, with the name of “Venetia et Histria”