Wonseong of Silla (r. 785-798, d. 798) was the 38th to rule the Korean kingdom of Silla. He was a twelfth-generation descendant of King Naemul. His father was Kim Hyo-yang, and his mother was Lady Gye-o, the daughter of Pak Chang-do. Wonseong's queen was Lady Yeonhwa, the daughter of Gakgan Kim Sin-sul.
In 780, Wonseong fought alongside his kinsman Kim Yang-sang to defeat the rebellion of Kim Ji-jeong. The rebellion left King Hyegong dead, and Kim took the throne as King Seondeok. The new king gave Wonseong the title of sangdaedeung. After Seondeok died without an heir, the nobles chose Wonseong as the new king.
After his death in 798, the king was buried south of Bongdeoksa.