Lothar III, Holy Roman Emperor

Lothair II
Portrait of Lothair in the Codex Eberhardi, Fulda monastery 1150/60
Holy Roman Emperor
Reign	1133–1137
Coronation	4 June 1133, Rome
Predecessor	Henry V
Successor	Frederick I
King of Germany (formally King of the Romans)
Reign	1125–1137
Coronation	13 September 1125, Aachen
Predecessor	Henry V
Successor	Conrad III
King of Italy
Reign	1125–1137
Predecessor	Henry V
Successor	Conrad III
Born	before 9 June 1075 Lutterloh, Duchy of Saxony
Died	4 December 1137 (1137-12-05) (aged 62) Breitenwang, Tyrol, Duchy of Bavaria
Burial	Königslutter
Spouse	Richenza of Northeim
Issue	Gertrude of Süpplingenburg
House	Supplinburg
Father	Gebhard of Supplinburg
Mother	Hedwig of Formbach
Religion	Roman Catholicism

Lothair II or Lothair III (before 9 June 1075 – 4 December 1137), known as Lothair of Supplinburg, was Holy Roman Emperor from 1133 until his death. He was appointed Duke of Saxony in 1106 and elected King of Germany in 1125 before being crowned emperor in Rome. The son of the Saxon count Gebhard of Supplinburg, his reign was troubled by the constant intriguing of the Hohenstaufens, Duke Frederick II of Swabia and Duke Conrad of Franconia. He died while returning from a successful campaign against the Norman Kingdom of Sicily.

Little is known of Lothair's youth. His father joined the Saxon Rebellion against the ruling Salian dynasty and died on 9 June 1075 in the Battle of Langensalza, fighting troops loyal to Emperor Henry IV. Shortly thereafter, Lothair was born posthumously at Unterlüß. In 1100 he married Richenza, daughter of Count Henry of Northeim and Gertrude of Brunswick, heiress of the Brunonids.

After years of purchasing lands or gaining them via inheritance or marriage alliances throughout Saxony, Lothair gained the domains of the House of Billung, the Counts of Northeim and the Brunonids, and became one of the dominant landowners in the North German duchy. He backed the emperor's son Henry V during the disempowerment of his father Henry IV and in turn was made Duke of Saxony upon the death of Magnus of Billung in 1106. Emboldened by the promotion and incensed over the imposition of a new tax on ducal lords, however, Duke Lothair subsequently revolted against Emperor Henry's rule and denied his ability to rule Saxony during the Investiture Controversy. He acted autonomously, vesting Count Adolf of Schauenburg with Holstein in 1110, was temporarily deposed in 1112 but reinstated after he tactically submitted himself to the rule of Henry V. In 1115 however, he joined the rebellious Saxon forces which defeated those of the Emperor in the Battle of Welfesholz. When in 1123 Henry V vested Count Wiprecht of Groitzsch with the Margraviate of Meissen, Lothair enforced the appointment of Conrad of Wettin and ceded the March of Lusatia to Count Albert the Bear.