Gertrud of Süpplingenburg (18 April 1115 – 18 April 1143) was the only child of Emperor Lothar III

Lothair III, Holy Roman Emperor

Lothair III of Supplinburg , was Duke of Saxony , King of Germany , and Holy Roman Emperor from 1133 to 1137. The son of Count Gebhard of Supplinburg, his reign was troubled by the constant intriguing of Frederick I, Duke of Swabia and Duke Conrad of Franconia...

 (Lothar of Süpplingenburg), Duke of Saxony, and his wife Richenza of Northeim

Richenza of Northeim

Richenza of Northeim was a member of the dynasty of the Counts of Northeim, and a German Empress.She was the daughter of Henry the Fat of Northeim and Gertrud of Brunswick of the Brunonen dynasty....

.

On 29 May 1127, she married the Welf, Henry the Proud

Henry X, Duke of Bavaria

thumb|right|Henry X in a much later engraving.Henry the Proud was the Duke of Bavaria , Duke of Saxony , and Margrave of Tuscany .-Life and reign:...

, who had been Duke of Bavaria since 1126. After the death of his father-in-law, Henry also became Duke of Saxony. He and Gertrud were the parents of Henry the Lion

Henry the Lion

Henry the Lion was a member of the Welf dynasty and Duke of Saxony, as Henry III, from 1142, and Duke of Bavaria, as Henry XII, from 1156, which duchies he held until 1180....

, Duke of Saxony and Bavaria.

After Henry's death in 1139, Gertrud married again, on 1 May 1142, to Henry II, the Margrave

Margrave

A margrave or margravine was a medieval hereditary nobleman with military responsibilities in a border province of a kingdom. Border provinces usually had more exposure to military incursions from the outside, compared to interior provinces, and thus a margrave usually had larger and more active...

 of Austria (died 1177).

She died on 18 April 1143, which was her 28th birthday. Henry later married his second wife, Theodora Komnene.