Blue Birthday (Korean: 블루버스데이; RR: Beullubeoseudei) is a South Korean drama web series produced by Naver subsidiary Playlist Studio. Directed by Park Dan-hee and co-written by Goo So-yeon and Moon Won-young, the series stars Kim Ye-rim as Oh Ha-rin and Yang Hong-seok as Ji Seo-jun. The series is a fantasy romance thriller drama in which the female protagonist, Oh Ha-rin, revisits the past through mysterious photos left by her first love, who died on her birthday 10 years ago. It premiered on July 23, 2021, on Naver TV and WeTV, and aired every Friday and Saturday at 19:00 (KST). It also became available on YouTube to audiences from South Korea on August 6, 2021.