Marcán mac Tommáin (died 653[1]) was the 15th king of the Uí Maine.
In his time the Uí Maine were allied and subject to the Ui Fiachrach Aidhne, a branch of the Connachta.
The annals record that Marcán was slain in a battle in Airthir Seola by Cenn Fáelad mac Colgan and Máenach mac Báethíne of the Ui Briun in 653.
[2] The Annals of Ulster refer to it as a battle of the Connachta.
Guaire's brother Loingsech mac Colmáin was ruling at this time and was being challenged by the Ui Briun.