Is there Demon Slayer season 3?

there has been no official announcement regarding a third season of the anime "Demon Slayer" (Kimetsu no Yaiba). However, it was announced that a new movie titled "Demon Slayer: Mugen Train" was released in Japan on October 16, 2020, and later released in other countries as well. The movie continues the story from where the first season left off and covers the Mugen Train Arc of the manga series.

 It's possible that a third season may be announced in the future, but at this time, there is no official confirmation. I recommend keeping an eye on official announcements from the production company, ufotable, and the official website and social media accounts of the "Demon Slayer" franchise for any updates.