Update (9/28/20): Crunchyroll and Funimation updated the premiere date to January 12.
Crunchyroll and Funimation announced that the first cour of That Time I Got Reincarnated as a Slime’s second season will premiere on January 12, 2021 in Japan.
The second cour will air in July 2021. That Time I Got Reincarnated as a Slime was originally slated for October 2020 but was delayed due to COVID-19. The series’ spin-off, The Slime Diaries, will also be pushed back to April 2021.
Crunchyroll will be simulcasting That Time I Got Reincarnated as a Slime season 2 to North America, Central America, South America, Europe, Africa, Oceania, and the Middle East. Concurrently, Funimation will also simulcast the anime and provide an English dub at a later date.
Crunchyroll describes the series as:
Corporate worker Mikami Satoru is stabbed by a random killer, and is reborn to an alternate world. But he turns out to be reborn a slime! Thrown into this new world with the name Rimuru, he begins his quest to create a world that’s welcoming to all races.
Source: Crunchyroll, Funimation