Lothair III was King of Germany and Holy Roman Emperor in the early 12th Century. He was notable for his succeeding to the German throne as the result of an election, not a hereditary succession.

He was born in June 1075 in Lutterloh, in the Duchy of Saxony. His father was Gebhard of Supplinburg, and his mother was Hedwig of Formbach. Not long after young Lothair was born, his father died at the Battle of Langensalza, fighting in the Saxon Rebellion against Holy Roman Emperor Henry IV.

Young Lothair grew up amidst many such battles, as the emperor strained to keep his hold on power. Lothair threw in his lot with the emperor's son, the future Henry V, in 1104. When son forced father's abdication and took his crown, Lothair found himself Duke of Saxony as reward for his loyalty. After awhile, in the eyes of many in the German duchies, Lothair among them, Henry V was not a big improvement over Henry IV. The emperor removed Lothair from power in 1112, replacing him with Otto of Ballenstedt; three years later, Lothair joined the revolt against Henry, helping the rebels defeat the imperial forces at the Battle of Welfesholz.

Henry's grip on power remained tenuous, but it remained, for another decade. The emperor died of cancer in 1125. Because Henry had no heir, genetic or designated, it was left to a royal electoral assembly to choose the next ruler. By this time, Lothair was the most powerful prince in Saxony and had the respect and support of many; the one rather large strike against him was that, despite having married Richenza of Northeim in 1100, he had no male heir and so, being in his 50s, was considered a risky choice to lead the kingdom. As well, Henry V did leave behind a nephew, Frederick, Duke of Swabia. However, Lothair found favor with enough electors and was crowned Lothair III*, King of Germany on Sept. 13, 1125. It helped a bit that he promised the hand of his only child, Gertrude, to Henry the Proud, son of the Duke of Bavaria, Henry the Black.

Frederick, of the House of Hohenstaufen, remained an adversary, claiming that he was entitled to his uncle's property; Lothair, on the other hand, claimed that as a handover from one monarch to the next.

Lothair, as King of Germany, had tremendous power in the Europe of the 12th Century. In the 1130s, he intervened in a dispute over the election of the pope, favoring Innocent II over Anacletus II. Lothair marched on Rome at the head of an army in support of Innocent II, who returned the favor by crowning Lothair first King of the Romans, on March 22, 1131, and then Holy Roman Emperor, on June 4, 1133.

Emperor Lothair returned to Germany in 1135 and defeated his Hohenstaufen enemies, in part because of the support of his son-in-law, Henry the Proud, by then Duke of Bavaria and later Margrave of Austria and the first Duke of Austria. The fighting ended with a promise from the Hofenstaufen forces to support Lothair in his next foray into Italy, to fight against Roger II of Sicily. Lothair's troops seized two major settlements on the island of Sicily but then refused to fight any more in the hot, sticky summer. Lothair sent them home and stayed on in Italy for a time.

He was on his way home in 1137 when he died, on December 3, in Breitenwang. Succeeding him as King of Germany was Conrad III. Succeeding him as Holy Roman Emperor was Frederick I.