Longobardia (, also variously Λογγιβαρδία, Longibardia and Λαγουβαρδία, Lagoubardia), was a Byzantine term for the territories controlled by the Lombards in Italy. In the 9th-10th centuries, it was also the name of a Byzantine province (thema) in southeastern Italy.

The term was traditionally used for the Lombard possessions, with the chronicler Theophanes the Confessor distinguishing between "Great Longobardia" (Μεγάλη Λογγοβαρδία, in Latin Langobardia major), namely the Lombard kingdom in northern Italy, and "Longobardia" (in Latin Longobardia minor), which comprised southern Italy, with the Lombard duchies of Spoleto, Salerno and Capua, the Byzantine possessions, and the city-states (Naples, Gaeta and Amalfi) under Byzantine suzerainty.

In its strictest and most technical sense, the name referred to the Byzantine thema which encompassed the modern Italian region of Apulia and parts of Basilicata, with Bari as its capital. Its exact origin and evolution are not entirely clear. Its establishment, perhaps first as a subordinate tourma of the thema of Cephalenia dates to ca. 876, when Bari was recovered by the Byzantines, who used it as a base to re-establish their control over southern Italy, lost in previous centuries to Lombards and Arabs. In ca. 893, it appears that it was administered jointly with other European themata of the Empire. A distinct strategos, whose presence would imply the province's elevation to a full thema, is only attested from 911 on.Kazhdan (1991), p. 1250 In 938 and 965 it also appears united with the thema of Calabria, although the duration of this arrangement is unclear. At any rate, after ca. 965, the two themata were permanently united into the new Catepanate of Italy, with the catepan's seat again at Bari.