Song Si-yŏl (Korean: 송시열; 1607–1689), also known by his art names Uam (우암) and Ujae (우재) or by the honorific Master Song (송자; 宋子; Songja), was a Korean philosopher and politician.

Born in Okcheon, North Chungcheong Province, he was known for his concern with the problems of the common people.

He served in governmental service for more than fifty years, and his name features over 3,000 times in the Annals of Joseon Dynasty, the greatest frequency that any individual is mentioned.

He was executed by the royal court for writing an inflammatory letter to the king.

He is also known as the calligrapher who inscribed an epitaph (Chungyeolmyobi Takboncheop) in dedication of Admiral Yi Sunsin, which is preserved at the Chungnyeolsa Shrine (historical site No.