The pagus or gau of Hasbania was a large early medieval territory in what is now eastern Belgium. It is now approximated by the modern French- and Dutch-speaking region called Hesbaye in French, or Haspengouw in Dutch — both being terms derived from the medieval one. Unlike many smaller pagi of the period, Hasbania apparently never corresponded to a single county. It already contained several in the 9th century. It is therefore described as a "Großgau" (large gau), like the Pagus of Brabant, by modern German historians such as Ulrich Nonn.
The Hesbaye region was a core agricultural territory for the early Franks who settled in the Roman Civitas Tungrorum, which was one of the main parts of early Frankish Austrasia, and later Lotharingia. The region was also culturally important, a central part of what is referred to in art history as the Mosan region. It contained a substantial Romanized population and the seat of a large bishopric, that played a role in converting northern Franks to Christianity, and in the secular administration of the area. The bishop's seat moved from the Roman capital at Tongeren to a new base at Liège, both of which were located in Hasbania.
Geographically, this region centres around a fertile plateau, which has been an agricultural region since the Neolithic. This higher ground forms a watershed between the Meuse and Scheldt drainage basins. In modern times "Hesbaye" and "Haspengouw" are geographical terms which are used for example in tourism and agriculture, and do not have the geo-political importance that they had in the early Middle Ages.