The Main Guard on O'Connell Street is one of the most significant seventeenth-century public buildings in Ireland. Built around 1675 to serve as a courthouse and administrative centre for the town, it is a rare survivor from that period — most buildings of comparable age in Munster were either demolished or substantially altered in later centuries.
The façade is elegant and restrained, with a first-floor arcade of rounded arches and a Tholsel-style design that reflects Dutch influence in Irish civic architecture of the time. The building has been carefully restored and is open to the public. The arcade at ground level was where merchants once traded, and the upper chamber served as the courts of the Palatinate of Ormond, which gave Clonmel a degree of legal independence from the Crown.