Horn is the fourth Korean studio album and seventh overall by South Korean girl group Apink. Marketed as "special album", it contains eleven tracks, including the 2021 single "Thank You" and the lead single "Dilemma". The album was released by IST Entertainment on February 14, 2022. It was the group's last album to feature group member Naeun, who withdrew from the group on April 8, 2022

On December 22, 2021, IST Entertainment announced Apink would be releasing a new album in February 2022.[2] On January 18, 2022, it was announced by YG Entertainment member Son Na-eun would not be participating in the album promotional activities with exception of filming for the album jacket and music video due "to difficulties in coordinating the schedule for her next project under discussion".On January 22, it was announced that Apink would be releasing Horn on February 14.The album was marketed as "special album" by IST Entertainment.Four days later, the track listing consisting of 11 tracks including previously released single "Thank You" and lead single "Dilemma" was released.On February 7, the highlight medley teaser video was released.The music video for "Dilemma" was released on February 11 and 13.