Louis I, also known as Louis the Pious or Louis the Fair, was a ruler of the Frankish empire in the 9th century. He was the son of Charlemagne and succeeded him as emperor after his death. Some synonyms for Louis I could include "Louis the Pious," which references his religious devotion and piety, "Louis the Fair," which acknowledges his reputation for justice and fairness in governing, and simply "Emperor Louis," which emphasizes his role as a powerful ruler. Additionally, he is sometimes referred to as "Louis the German" because of his efforts to strengthen ties with the eastern regions of the empire.