The Battle of Prosperous is the name given to a military engagement between the forces of the British Crown and the United Irishmen during the 1798 rebellion. Prosperous, County Kildare, a recently founded (1780) cotton-manufacturing town, was attacked shortly after the outbreak of the 1798 rebellion at 2 a.m on 24 May 1798 by a rebel force about 60 strong which targeted the British garrison consisting of Cork militia and a detachment of a Welsh regiment, the "Ancient Britons".
The rebel entry into the town was preceded by the infiltration of a small vanguard who, possibly aided by female sympathisers within, scaled the walls of the militia barracks, killed the sentries and opened the gate. The barracks was quickly surrounded and attacked by hundreds of rebels who repulsed an attempt by the militia to break out, killing the militia commander, Captain Swayne. The remainder of the garrison were trapped in the upper barracks which was then torched causing the desperate soldiers to leap from windows onto the waiting pikes. About 40 of the military were slain but the next day, members of the Ancient Britons participated in the retaliatory massacre of 34 suspected United Irishmen at Dunlavin Green, Co. Wicklow.
Prosperous remained under rebel control until 19 June when retaken by troops under the command of Colonel Stewart who boasted of destroying "this receptacle of rebellion".