Crisis on Infinite Earths is the name of the sixth annual Arrowverse crossover event between Supergirl, Batwoman, The Flash, Arrow, and DC's Legends of Tomorrow. Additionally, events in the Black Lightning episode "The Book of Resistance: Chapter Four: Earth Crisis" and a two-issue comic, Crisis on Infinite Earths Giant, tie into the crossover. It began over three nights in December 2019 from December 8 to December 10 and concluded on January 14, 2020.