Engelbert III was the Margrave of Istria. from 1124 until his death. He was a Sponheimer, the eldest son of Engelbert II and Uta of Passau. He succeeded his father in Istria when his father was raised to the Duchy of Carinthia

Duchy of Carinthia

The Duchy of Carinthia was a duchy located in southern Austria and parts of northern Slovenia. It was separated from the Duchy of Bavaria in 976, then the first newly created Imperial State beside the original German stem duchies....

. He is sometimes numbered Engelbert II of Istria.

From 1135 to 1137 Engelbert was Margrave of Tuscany. In 1156, he witnessed the granting of the Privilegium Minus

Privilegium Minus

The Privilegium Minus is a document issued by Emperor Frederick I on September 17, 1156. It included the elevation of the Margraviate of Austria to a Duchy, which was given as an inheritable fief to the House of Babenberg. Its recipient was Frederick's paternal uncle Margrave Henry II Jasomirgott...

creating the Duchy of Austria.

Engelbert married Matilda of Sulzbach

Matilda of Sulzbach

Matilda of Sulzbach was the wife of Engelbert III of Istria. Different dates of death are given in the necrologies of Baumburg Abbey and two monasteries of Salzburg. -Family:...

, youngest daughter of Berengar I of Sulzbach. He was thus a brother-in-law of Gertrude, wife of Conrad III of Germany

Conrad III of Germany

Conrad III was the first King of Germany of the Hohenstaufen dynasty. He was the son of Frederick I, Duke of Swabia, and Agnes, a daughter of the Salian Emperor Henry IV.-Life and reign:...

, and Irene

Bertha of Sulzbach

Bertha of Sulzbach was the first wife and Empress of Byzantine Emperor Manuel I Comnenus.-Family:...

, wife of Manuel I Comnenus. Matilda died late in 1165.