Since Thunder founded ThunderClan, Wind founded WindClan, River founded RiverClan, and Shadow founded ShadowClan, a cat named Sky founded SkyClan. However, SkyClan was driven out of its original territory in the forest. When SkyClan was all but extinct, Firestar helped the clan re-form.
By the way Sky(founder of skyclan) is not the same sky as the one firestar met in firestars quest
Clear Sky 18.104.22.168 19:07, October 4, 2015 (UTC) Shorewillow