Queen Seondeok follows the extraordinary life of Princess Deokman, who is abandoned as an infant due to a prophecy and grows up unaware of her royal lineage. She eventually returns to the kingdom of Silla, discovers her true identity, and engages in a fierce political and psychological war against the ruthless and ambitious royal concubine Mishil. Through strategic brilliance and the unwavering loyalty of figures like Kim Yushin and Bidam, Deokman overcomes impossible odds to become the first female monarch in Korean history. The series explores themes of power, sacrifice, loyalty, and statecraft against the backdrop of the Three Kingdoms period of Korea. As Deokman rises from a humble background to the ultimate seat of power, she must master the art of governance while navigating devastating personal betrayals and complex romantic entanglements.