Moon Seong-hyun is a South Korean actor born on June 2, 2006. He is known for playing the younger versions of male leads in several popular K-dramas, beginning his career in 2021. He is managed by FNC Entertainment.

He first appeared in the 2021 dramas Vincenzo and Hometown Cha-Cha-Cha. He gained significant recognition for his role as the young Seo Yul in the fantasy drama Alchemy of Souls and as Prince Simso in the historical series Under the Queen's Umbrella. His emotional performance in the latter received high praise.

In 2024, Moon took on his first starring role in the web drama The Chairman of Class 9.he was nominated for "Best Young Actor" at the 60th Baeksang Arts Awards and won "Best Young Actor" at KBS Drama Awards with Beauty and Mr. Romantic.