Wonseong of Silla (r. 785–798, died 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.

Wonseong of Silla ruled out the Resolution of the Ji-jeong with the Yang-sang in 780 before becoming king. He killed Hyegong of Silla and contributed to the throne. From this point of view, he is a figure closely related to his appearance and has been opposed to the monarchy of the royal family since King Gyeongdeok. Hyegong of Silla was appointed to Sangdaedeung in 780 (King Seongdeok 1) for his work to calm down the turmoil at the end of King Hyegong's reign.

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.

In 787, Wonseong sent tribute to Tang China and requested a title. In 788, he established the national civil service examination for the first time, on the Tang model.

After his death in 798, the king was buried south of Bongdeoksa.

元聖王（？ - 798年）；姓金名敬信，是新羅第三十八代君主，一吉飡金孝讓之子，奈勿王的十二世孫，母繼烏夫人樸氏。宣德王無嗣，群臣欲立王族子金周元，因大雨河水暴漲不得渡，議者曰：人君大位，有關天命，非人謀所及。今日暴雨，天其不欲立周元乎！于是上大等金敬信被擁為王，立之而雨止，國人皆呼萬歲。在位十五年，諡元聖，遺命燒柩於奉德寺南。

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