Colla mac Fergusso
Colla mac Fergusso was a possible King of Connacht from the Uí Briúin branch of the Connachta. He was the son of Forggus mac Cellaig, a previous king. The sept of Uí Briúin Ai he belonged to was the Síl Cellaig of Loch Cime named for his grandfather Cellach mac Rogallaig.
Though omitted from king lists such as the Book of Leinster, he is called king at his death obit in the Annals of Innisfallen. However, the Annals of Ulster say that Muirgius mac Tommaltaig became king after defeating Cináed mac Artgail at the Battle of Sruth Cluana Argai in 792. His death is recorded in this annal as King of Uí Briúin.
Colla was the last king from the Síl Cellaig sept. This sept was later displaced from this area by the Uí Briúin Seóla.
