Taejo was the founder and first ruler of the Joseon Dynasty in Korea, reigning from 1392 to 1398. Born Yi Seong-gye, he came to power by overthrowing the Goryeo Dynasty. His reign marked the end of Goryeo's 475-year rule and the beginning of Joseon, which he officially established in 1393.

Taejo's reign was characterized by efforts to maintain continuity with the past. He retained many institutions and officials from the Goryeo era and prioritized improving foreign relations. He successfully re-established diplomatic ties with Japan and improved relations with Ming China, refusing to respond to raids from Chinese bandits and sending envoys to inform the Ming court of the dynastic change. Envoys were also sent to Japan, rekindling amicable connections, and he received envoys from the Ryūkyū Kingdom and Siam.

In 1394, Taejo established the new capital at Hanseong, present-day Seoul. However, his reign was marred by familial strife regarding the succession to the throne. Despite Yi Bang-won, Taejo's fifth son, contributing significantly to his father's rise to power, he was overlooked as the heir due to Taejo's advisors favoring other sons. This led to the 'First Strife of Princes' in 1398, where Yi Bang-won revolted, killing key figures opposing him, including Jeong Do-jeon and Queen Sindeok's sons.

Shocked by the violence among his sons and grieving the loss of his second wife, Queen Sindeok, Taejo abdicated in favor of his second son, Yi Bang-gwa, who became King Jeongjong. Taejo retired to Hamhung Royal Villa, distancing himself from Yi Bang-won (later King Taejong). Contrary to popular belief, Taejo did not execute emissaries from Yi Bang-won; they died coincidentally in revolts.

In 1400, King Jeongjong named Yi Bang-won as the heir and abdicated, leading to Yi Bang-won's ascension as King Taejong. Taejo's reign, though short, was pivotal in establishing the Joseon Dynasty and laying the groundwork for subsequent transformations in Korean history.