The Tomb of King Muryeong calls him King Sama (斯麻), and records his birth year as 462.
The Samguk Sagi calls him King Muryeong, with the personal name (휘) of Sama (斯摩). He is described as the second son of the 24th king Dongseong. He became king when Dongseong was assassinated by the court official Baekga. The following year, he crushed a planned rebellion by Baekga.