The sole member of the house of Supplinburg to hold the titles, Lothar II (1075-1137) became duke of Saxony in 1106, king of Germany in 1125 and Holy Roman Emperor in 1133.
Lothar faced opposition through most of his reign from Frederick II, the Hohenstaufen duke of Swabia, whom he had defeated in the election to the kingship (the usual preliminary to accession as emperor), and Frederick's brother Conrad III.
Elected as rival king (1127), Conrad submitted to Lothar only in 1135. After Lothar's death, he was elected (1138) king of the Romans, ruling as emperor in all but name, though he was never crowned as such.
The son of Gebhard, count of Supplinburg, and Hedwig, countess of Formbach, Lothar married Richensia of Nordheim. Their daughter Gertrude married Henry the Proud, duke of Saxony and Bavaria. Lothar is entombed in the monastery church of Königslutter.
LothairIII of Supplinburg (1075 – 1137), was Duke of Saxony (1106), King of Germany (1125), and Holy Roman Emperor from 1133 to 1137.
LothairIII is thus seen as a successor of Emperor Lothair I (ruled 843-855) and King Lothair II of Lotharingia (ruled 855-869), most of whose kingdom was eventually absorbed into Germany.
The force Lothair took with him into Italy in 1132 was not strong, due to his leaving troops in Germany to prevent the Hohenstaufen from revolting.
He accompanied Innocent to Rome, successfully resisting the proposal to reopen negotiations with Anacletus, who held the castle of Sant' Angelo and, with the support of Roger of Sicily, was too strong The Cistercians of this branch of the order were commonly known as Bernardines.
Lothair, though crowned by Innocent in St Peter's, could do nothing to establish him in the Holy See so long as his own power was sapped by his quarrel with the house of Hohenstaufen.
In 1137, the year of Lothair's last journey to Rome, Bernard was back in Italy again; at Monte Cassino, setting the affairs of the monastery in order, at Salerno, trying in vain to induce Roger of Sicily to declare against Anacletus, in Rome itself, agitating with success against the antipope.