Reign is cancelled by The CW

[kimmy_kun]

#Reign will no longer reign over the CW - after next season, that is. https://t.co/GbTUmaPx1i pic.twitter.com/XToi6giBJu
- Variety (@Variety) December 8, 2016

The upcoming season 4 will be its last.

Source

Surprised it made it past 13 episodes, tbh. And I say this as someone who watches this mess.