King Lothair III was a medieval ruler who reigned from 1125 to 1137. He was a member of the Salian dynasty and became the Holy Roman Emperor in 1133. His reign was marked by conflicts with rival factions and struggles for power within the empire. Lothair III is known for his efforts to strengthen the authority of the Holy Roman Empire and for his involvement in the Investiture Controversy, a significant conflict between the church and state over the appointment of bishops. His reign contributed to the ongoing development of imperial authority in Europe during the 12th century.