<P> `` Crisis on Earth - X '' is the fourth annual Arrowverse crossover event , featuring episodes of the live - action television series Supergirl , Arrow , The Flash , and Legends of Tomorrow on The CW . The crossover began on November 27 , 2017 , with Supergirl and Arrow , and concluded on November 28 , with The Flash and Legends of Tomorrow . In `` Crisis on Earth - X '' , Barry Allen and Iris West 's friends come to Central City for their wedding , only to be interrupted when villains from Earth - X disrupt the proceedings . </P>
<P> `` Crisis on Earth - X '' is the fourth annual Arrowverse crossover event , featuring episodes of the live - action television series Supergirl , Arrow , The Flash , and Legends of Tomorrow on The CW . The crossover began on November 27 , 2017 , with Supergirl and Arrow , and concluded on November 28 , with The Flash and Legends of Tomorrow . In `` Crisis on Earth - X '' , Barry Allen and Iris West 's friends come to Central City for their wedding , only to be interrupted when villains from Earth - X disrupt the proceedings . </P>
when does the flash cross over with arrow
when does the flash cross over with arrow
November 27 , 2017
November 27 , 2017