<P> Legends of Tomorrow is an American action - adventure television series developed by Greg Berlanti, Marc Guggenheim, Andrew Kreisberg and Phil Klemmer, who are also executive producers along with Sarah Schechter and Chris Fedak; Klemmer serves as showrunner . The series airs on The CW and is a spin - off from Arrow and The Flash, existing in the same fictional universe . </P> <P> As of April 9, 2018, 51 episodes of Legends of Tomorrow have aired, concluding the third season . On April 2, 2018, The CW renewed the series for a fourth season, which is set to premiere on October 22, 2018 . </P> <Table> <Tr> <Th_colspan="2"> Season </Th> <Th_colspan="2"> Episodes </Th> <Th_colspan="2"> Originally aired </Th> <Th_colspan="2"> Nielsen ratings </Th> </Tr> <Tr> <Th> First aired </Th> <Th> Last aired </Th> <Th> Rank </Th> <Th> Average viewership (in millions) </Th> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> </Td> <Td_colspan="2"> 16 </Td> <Td_colspan="1"> January 21, 2016 (2016 - 01 - 21) </Td> <Td> May 19, 2016 (2016 - 05 - 19) </Td> <Td> 135 </Td> <Td> 3.16 </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> </Td> <Td_colspan="2"> 17 </Td> <Td_colspan="1"> October 13, 2016 (2016 - 10 - 13) </Td> <Td> April 4, 2017 (2017 - 04 - 04) </Td> <Td> 141 </Td> <Td> 2.57 </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> </Td> <Td_colspan="2"> 18 </Td> <Td_colspan="1"> October 10, 2017 (2017 - 10 - 10) </Td> <Td> April 9, 2018 (2018 - 04 - 09) </Td> <Td> 170 </Td> <Td> 2.24 </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> </Td> <Td_colspan="2"> 16 </Td> <Td_colspan="1"> October 22, 2018 (2018 - 10 - 22) </Td> <Td> TBA </Td> <Td> TBA </Td> <Td> TBA </Td> </Tr> </Table> <Tr> <Th_colspan="2"> Season </Th> <Th_colspan="2"> Episodes </Th> <Th_colspan="2"> Originally aired </Th> <Th_colspan="2"> Nielsen ratings </Th> </Tr>

How many episodes in season 3 of dc legends of tomorrow