Seongdeok Daewang (reigned 702–737) is the thirty-third king of the ancient Korean kingdom of Silla.

He is the second son of King Sinmun, and the younger brother of King Hyoso.

In 704 Seongdeok marries Lady Baeso (Queen Seongjeong), the daughter of Gim Wontae.

In 715 their son, Junggyeong, is named Crown Prince and heir presumptive.

Shortly thereafter, and for reasons unclear but quite likely having to do with a power struggle at court between the king and the clan of the queen, Queen Seongjeong is evicted from the palace in 716.

As further evidence of a possible power struggle, the next year Junggyeong dies under circumstances that remain unknown.

Following the fall from favor of his first wife, King Seongdeog marries Sodeok in 720, the daughter of the minister Gim Sun-won.

Kings Hyoseong and Gyeongdeok are among the children of Seongdeok and Sodeok.