Seongdeok of Silla (?-737, r. 702-737 was the 33rd king of that ancient Korean kingdom. He was the second son of King Sinmun, and the younger brother of King Hyoso. After the death of his first wife, Seongjeong, he married Sodeok, the daughter of the minister Gim Sun-won. Kings Hyoseong and Gyeongdeok were among the children of King Seongdeok and Sodeok.
According to the Samguk Sagi, Seongdeok invented Korea's first water clock in 718. Lee (1984) contends that in his reign, "the paramount authority of the throne was finally secured, and with this accomplished the kingdom at last was able to enjoy unaccustomed domestic tranquility."
Silla absorbed the Gaya confederacy, annexing Geumgwan Gaya in 532 and conquering Daegaya in 562, thereby expanding its borders to the Nakdong River basin.
The capital of the Silla kingdom was Gyeongju.
Silla tombs took the form of a stone chamber which was surrounded by a soil mound.