After the season 2 of One-Punch Man, The anime just disappeared into thin air and it’s high time to renew the third season.
Right now there’s absolutely no news about it but we can expect it to air in summer 2023.
Season 3 will adapt the Monster Association Arc from manga and Saitama will face Orochi in it.
Judging from the previous seasons, The next one will have around 12 episodes.
If you want to read One-Punch Man then volume 17 is exactly where season 2 ended.