Mountbellew is known in Irish as 'An Creagan', the little rock, or a rocky or stony place.  The town owes its name to the Bellew family which originated in Belleau, France and came to Ireland through England at the time of the Anglo-Norman invasion but did not achieve prominence until the end of the fourteenth century.  They settled in Meath and Louth.  The Bellews of Mountbellew are descended from James Bellew of Bellewstown, County Meath.

The Franciscan Brothers came to Mountbellew, Co Galway from Milltown, in Dublin, in the year 1818.  The Bellew family invited them and gave them resources of land and a house to get established.The Brothers taught a free primary school until 1884. In 1875 they opened a secondary school (boarding) and in 1898 a special Department in the school was set up to prepare students for Teacher Training Colleges.