Duty After School (Korean: 방과 후 전쟁활동) is a 2023 South Korean military sci-fi thriller dystopian teen drama television series created by Lee Nam-gyu [ko], written by Yoon Soo and directed by Sung Yong-il. The series stars an ensemble cast including Shin Hyun-soo, Lee Soon-won, Im Se-mi, Kwon Eun-bin, Kim Ki-hae, Kim Min-chul, Kim So-hee, Kim Su-gyeom, Kim Jung-lan, Moon Sang-min, Shin Myung-sung [ko], Shin Su-hyun, Shin Hye-ji, Ahn Da-eun, Ahn Do-gyu, Yeo Joo-ha [ko], Oh Se-eun, Woo Min-gyu, Yoon Jong-bin [ko], Lee Yeon, Ji Min-hyuk, Choi Moon-hee [ko], Hong Sa-bin, and Hwang Se-in. Based on the webtoon of the same name by Ha Il-kwon, which was later serialized on Naver Webtoon, it follows students who are conscripted as cadets to combat mysterious purple alien objects that appear in Earth’s skies and threaten humanity. It was released from March 31 to April 21, 2023, on TVING's Fridays at 16:00 (KST). It is also available for streaming on Viu and Viki in selected regions.

The series was divided into two parts: Part 1 was released on March 31, 2023, while Part 2 on April 21, 2023.

Duty After School tells the story of the senior students at Sungjin High School as they are conscripted to fight against the attack of a group of mysterious creatures that have covered the sky.

Studio Dragon together with director Sung Yong-il, who directed Class of Lies (2019), and writer Lee Nam-gyu, who wrote The Light in Your Eyes (2019), produced the popular webtoon Duty After School [ko] into a drama. Production begun with the goal of broadcasting in 2022.

According to Bloter, the series was scheduled to be included as TVING's original content and Studio Dragon considered the possibility that it would be included as a Netflix original series.

Shin Hyun-soo and Hwang Se-in confirmed their appearance for the series in August and October 2021, respectively.

In February 2023, the cast lineup and the release date of the series were revealed.

Principal photography began in August 2021 and ended in March 2022.