<P> Supergirl is an American superhero action - adventure drama television series developed by Ali Adler, Greg Berlanti, and Andrew Kreisberg, based on the DC Comics character Supergirl, created by Otto Binder and Al Plastino, that originally aired on CBS and premiered on October 26, 2015 . Supergirl is a costumed superheroine who is the biological cousin to Superman and one of the last surviving Kryptonians . The series was officially picked up on May 6, 2015, and received a full season order on November 30, 2015 . The series moved from CBS to The CW from its second season onwards . </P> <P> As of June 18, 2018, 65 episodes of Supergirl 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 14, 2018 . </P> <Table> <Tr> <Th_colspan="2"> Season </Th> <Th_colspan="2"> Episodes </Th> <Th_colspan="3"> Originally aired </Th> <Th_colspan="2"> Nielsen ratings </Th> </Tr> <Tr> <Th> First aired </Th> <Th> Last aired </Th> <Th> Network </Th> <Th> Rank </Th> <Th> Average viewership (in millions) </Th> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> </Td> <Td_colspan="2"> 20 </Td> <Td_colspan="1"> October 26, 2015 (2015 - 10 - 26) </Td> <Td> April 18, 2016 (2016 - 04 - 18) </Td> <Td> CBS </Td> <Td> 39 </Td> <Td> 9.81 </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> </Td> <Td_colspan="2"> 22 </Td> <Td_colspan="1"> October 10, 2016 (2016 - 10 - 10) </Td> <Td> May 22, 2017 (2017 - 05 - 22) </Td> <Td> The CW </Td> <Td> 129 </Td> <Td> 3.12 </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> </Td> <Td_colspan="2"> 23 </Td> <Td_colspan="1"> October 9, 2017 (2017 - 10 - 09) </Td> <Td> June 18, 2018 (2018 - 06 - 18) </Td> <Td> 154 </Td> <Td> 2.82 </Td> </Tr> </Table> <Tr> <Th_colspan="2"> Season </Th> <Th_colspan="2"> Episodes </Th> <Th_colspan="3"> Originally aired </Th> <Th_colspan="2"> Nielsen ratings </Th> </Tr>

When did season 3 of supergirl come out