Supernatural is a series.
Castiel [ ˌkæstiˈɛl ] is a fictional character portrayed by Misha Collins on the CW Television Network 's American television series Supernatural . Supernatural (U.S. TV series) . Originally , Kripke planned the series for three seasons but later expanded it to five . With its eleventh season , Supernatural became the longest-running American fantasy series . The series was renewed for a twelfth season , which aired from October 13 , 2016 , to May 18 , 2017 .