<P> Supergirl is an American superhero action - adventure drama television series developed by Ali Adler, Greg Berlanti and Andrew Kreisberg (the latter two having previously created Arrow and The Flash) that originally aired on CBS and premiered on October 26, 2015 . It is based on the DC Comics character Supergirl (Kara Zor - El), created by Otto Binder and Al Plastino, and stars Melissa Benoist in the title role . Supergirl is a costumed superheroine who is the biological cousin to Superman and one of the last surviving Kryptonians . </P> <P> The series was officially picked up on May 6, 2015, after receiving a series commitment in September 2014, and received a full season order on November 30, 2015 . On May 12, 2016, Warner Bros. Television announced that the series had been renewed for a second season and that it would move from CBS to The CW . It debuted on October 10, 2016 . On January 8, 2017, The CW renewed the series for a third season, which is scheduled to debut on October 9, 2017 . As of May 22, 2017, 42 episodes of Supergirl have aired, concluding the second season . </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> </Table>

When do new episodes of supergirl come out