Yoon Seo-A (Korean: 윤서아; born September 30, 2000), born Im Sun-woo (임선우), is a South Korean actress. She made her television debut in 2018 with the drama Bad Papa and gained recognition for her role as Seo Ji-wan in the 2021 Netflix series Nevertheless.

Yoon has since appeared in a variety of television productions, including Love Revolution (2020), True Beauty (2020), Juvenile Justice (2022), Soundtrack #1 (2022), Bloody Heart (2022), and Today’s Webtoon (2022). In 2024, she portrayed Chae Young-ji in Goodbye Earth and Baek Yi in The Tale of Lady Ok.