Surprise to anyone, Demon Slayer 3 season 3 officially occurred because it was announced after the final season 2.
With the second season which includes the ARC Ending entertainment district, Ufotable announces that the third season is on its way. Demon Slayer Season 3 will focus on the village sword Arc and will see the main return with director Haruo Sotozaki and head of the head of the head Akira Matsushima will also return. There is no release date set for the show but two poster characters are revealed.
https://www.youtube.com/watch?v=4lkSNzH9nqw
Demon Slayer began as a series of manga written and illustrated by Koyoharu Getouge. It was serial in Weekly Shonen Jump from February 2016 to May 2020. Anime was also adapted into a video game by CyberConnect2 titled Demon Slayer: The Hinokami Chronicles. Crunchyroll and Funimation series streams with funimasi also carry the dubbed version.