Engelbert III[a] (died 6 October 1173), a member of the Rhenish Franconian House of Sponheim, was Margrave of Istria[1] from 1124 until his death.
[2] When his father succeeded his elder brother Henry as Duke of Carinthia, Engelbert III received the margravial title in Istria.
[3] In turn, Engelbert was vested with the Imperial March of Tuscany, but was succeeded by the Welf duke Henry X of Bavaria already in 1137.
Engelbert attended the 1156 Imperial Diet in Regensburg, where he witnessed the granting of the Privilegium Minus by Emperor Frederick Barbarossa, elevating the March of Austria to a duchy.
In 1140 Engelbert had married Matilda, youngest daughter of the Bavarian count Berengar II of Sulzbach.