The Battle of Ballinamuck marked the defeat of the main force of the French incursion during the 1798 Rebellion in Ireland.
The victory of General Humbert at Castlebar, despite gaining him c. 5,000 Irish recruits had not led to a renewed outbreak of the rebellion as hoped. A massive British army of some 26,000 men was assembled under the new Viceroy Lord Cornwallis and was steadily moving towards his forces. Abandoning Castlebar, Humbert moved towards Ulster with the apparent intention of igniting a rising there but after defeating a blocking force of British troops at Collooney in Sligo he altered course following reports that rebellions had broken out in Westmeath and Longford.
Humbert crossed the Shannon at Ballintra on 7 September and stopping at Cloone that evening, was halfway between his landing-point and Dublin. News reached him of the defeat of the Westmeath and Longford rebels at Wilsons Hospital and Granard from the trickle of rebels who had survived the slaughter and reached his camp. With Cornwallis' huge force blocking the road to Dublin, facing constant harassment of his rearguard and the pending arrival of General Lake's command, Humbert decided to make a stand the next day at the townland of Ballinamuck on the Longford/Leitrim border.
Humbert faced overwhelming numbers. General Lake was close behind with 14,000 men; the new Viceroy, Lord Cornwallis, on his right at Carrick-on-Shannon with 15,000. The battle began with a short artillery duel followed by a dragoon charge on exposed Irish rebels. There was a brief struggle when French lines were reached which only ceased when Humbert signalled his intention to surrender and his officers ordered their men to lay down their muskets. This conventional battle lasted little more than half an hour.
While the French surrender was being taken the 1,000 or so Irish allies of the French under Colonel Teeling, an Irish officer in the French army, held onto their arms without signalling the intention to surrender or being offered terms. An attack by infantry followed by a dragoon charge broke and scattered the Irish who were ruthlessly pursued with much slaughter.
96 French officers and 748 men were taken prisoner. British losses were initially reported as 3 killed and 16 wounded or missing, but the number of killed alone was later reported as 12. Approximately 500 Irish lay dead on the field, 200 prisoners were taken in the mopping up operations, almost all of whom were later hanged, including Matthew Tone, brother of Wolfe Tone. The prisoners were moved to Carrick-on-Shannon, St Johnstown, today's Ballinalee, where most were executed in what is known locally as Bully's Acre.
Humbert and his men were taken by canal to Dublin and repatriated. The British army then slowly spread out into the rebel held "Republic of Connaught" in a brutal campaign of killing and house burning which reached its climax on 23 September when Killala was stormed and retaken with much slaughter. Members of the French inspired "Republic of Connaught" such as George Blake, were hunted down and hanged with many other suspected insurgents including Fr Andrew Conroy who led French and Irish forces to Castlebar though the Windy Gap, a passage though the Mountains.
The catastrophe at Ballinamuck left a strong imprint on social memory and featured strongly in local folklore. Numerous oral traditions were later collected about this episode, principally in in the 1930s by the historian Richard Hayes and by the Irish Folklore Commission.