One-reeler / Act IV is the fourth and final extended play by South Korean–Japanese girl group Iz*One. It was released through Off the Record Entertainment on December 7, 2020. The album is available in three versions: Scene #1, Scene #2 and Scene #3, and consists of six tracks including the lead single, "Panorama".

Iz*One was a South Korean–Japanese girl group formed through the Mnet reality competition show Produce 48. The group was composed of twelve members: Jang Won-young, Sakura Miyawaki, Jo Yu-ri, Choi Ye-na, An Yu-jin, Nako Yabuki, Kwon Eun-bi, Kang Hye-won, Hitomi Honda, Kim Chae-won, Kim Min-ju and Lee Chae-yeon. They were managed by Off the Record and Swing Entertainment.