ASASSN-V J213939.3-702817.4 (also known as ASAS-SN-V J213939.3-702817.4 and J213939.3-702817.4) is a star, previously non-variable, found to be associated with an unusual, deep dimming event that was uncovered by the All Sky Automated Survey for SuperNovae (ASAS-SN) project, and first reported on 4 June 2019 in The Astronomer's Telegram.

[2][3][4] The star, in the constellation of Indus, about 3,630 ± 110 light-years (1,113 ± 33 pc)[3][6] away, was first observed on 15 May 2014 (UT) by ASAS-SN, and, as of 4 June 2019, has resulted in more than 1780 data points, including a quiescent mean magnitude of g~12.95.

[2] On 4 June 2019, the star was reported to have dimmed gradually from g~11.96 at HJD 2458635.78, to g~14.22 at 4458837.45, and, as of 4 June 2019, seems to be returning to its quiescent state of g~13.29 at HJD 2851634.89.

[2] According to astronomer Tharindu Jayasinghe, one of the discoverers of the deep dimming event, "[The star has] been quiescent for so long and then suddenly decreased in brightness by a huge amount ... Why that happened, we don't know yet.

"[4]