Seven kilometres north of Clonmel is the monastic settlement at Donaghmore. A Hiberno-Romanesque Church was built here in the 12th century.
In 916 The Annals of Ulster record that a battle between the Uí Néill and the Vikings took place in the Clonmel area. There were 100 men killed in this battle.
Sometime in 1205 or 1206 William de Burgo was granted the lordship of the Manors of Clonmel, Kilsheelan and Kilfeacle. Two decades later, his son, Richard de Burgo, obtained from King Henry III authority to hold an annual fair in Clonmel.
In 1265 a Swiss man called De Grandison became Sheriff of Tipperary and Lord of the Manor of Clonmel. It was he who commenced the building of the town walls.
In 1249 the Black Death visited Clonmel. In the town there are plague pits at the sites of the Churches of St Nicholas and St Stephen.
Clonmel became a Free Borough by Royal Charter on July 5th 1608.
Oliver Cromwell captured Clonmel in 1650 after a three week siege. Although he achieved his objective his army suffered an estimated 2,500 casualties.
William of Orange’s army entered Clonmel without resistance on July 20th 1690 on his way to Limerick.
In 1831 the population of Clonmel was 17,838. By the start of the Potato Famine in 1841 it had fallen to 13,505. In 1871, there was just over ten thousand people left living in the town.
The Irish Labour Party was founded in Clonmel in 1912.
The Great War saw hundreds of Clonmel men fighting in France, Gallipoli and in Mesopotamia. Approximately 150 were killed.
In 1922 Clonmel was captured by the Free State Army from Anti-Treaty forces who burned the Army and Police barracks as they withdrew from the town.