Colclough, John Henry (1769–1798), insurgent leader, was born 15 June 1769, the son of Thomas Francis Colclough and his wife Catherine McMahon, of Ballyteigue, Bargy, Co. Wexford. He worked as a physician, leased a substantial landed estate, and was one of the county's most prominent catholics. During the 1790s he pressed strongly for the repeal of the penal laws and the advancement of catholics, and he probably joined the United Irishmen about 1795. He was described as being of middle size with ‘polished manners’ and a ‘rather a long visage . . . of a cheerful aspect’ (Madden, 495). Jonah Barrington (qv) mentioned him as being present at a dinner attended by Wexford and national United Irish leaders on 27 April 1798 at Bargy Castle, home of Beauchamp Bagenal Harvey (qv), at which strong revolutionary sentiments were expressed.
After the outbreak of rebellion in Wexford on 26 May, Colclough's name was revealed under torture to the military as a United Irish leader by Anthony Perry (qv). Colclough was arrested at his home and imprisoned in Wexford jail on 27 May 1798. On 29 May he and Edward Fitzgerald (qv) were sent as envoys to the insurgents camped outside Enniscorthy at Vinegar Hill to persuade them to lay down their arms, while Harvey was detained as a hostage. The rebels, however, were flushed with their victories at Oulart Hill and Enniscorthy and had no intention of surrendering; instead they sent Colclough back to Wexford to tell the garrison that they were about to march on the town. This message caused great consternation and the garrison prepared to leave, believing the town to be indefensible. Colclough then asked to be allowed to attempt to persuade United Irish units in Forth and Bargy against joining the rising, and after riding through these areas and spending the night at home, he returned to Wexford on 30 May to take his place in prison to secure Harvey's release. Travelling to the town in a phaeton with his wife, he was met by the retreating garrison and used as a hostage before being released. On entering the town the following day, he was appointed a colonel in the rebel army. He remained in Wexford until called on by Harvey (who had been chosen as commander of the insurgents) to join in the attack on New Ross (5 June). Colclough's battalion was assigned to attack the Market Gate, but they faltered at the beginning of the advance and soon retreated. Throughout the insurrection Colclough was a reluctant rebel, unwilling to commit himself, and he seems to have hoped for an early end to hostilities. He was present at the battle of Goff's Bridge (Foulkesmill) (20 June), and disrupted the rebel strategy by leading his battalion away on an unauthorised manoeuvre to cut off the enemy's line of retreat.
After Wexford town was retaken by crown forces on 21 June, Colclough and his wife fled to the Greater Saltee Island, where they hid in a cave; they were later joined by Harvey. However, they had been spotted rowing out to the island and the authorities were notified. A military search party led by Dr Richard Waddy, a Wexford physician and yeoman who knew Colclough and Harvey, arrived at the island on 24 June. By flogging an old man who lived on the island they discovered the fugitives’ hideout and brought them back to Wexford town. At his court-martial (27 June), Colclough pleaded that he had acted under duress and had not participated in any fighting, but Gen. Lake (qv) was determined to make examples of gentleman rebels, and he was found guilty of treason. Before his execution, it was reported that Colclough had toasted the king and constitution and said he hoped his fate would be a warning to others. He was hanged and beheaded on Wexford bridge 28 June 1798. His severed head and those of other executed insurgents were displayed on spikes at Wexford courthouse. His body was interred in the old burial ground of St Patrick's church, Wexford.
He married Elizabeth Berry in 1796 and had one child. Since his property was mostly leasehold, no attainder was issued against him. He was a cousin of Caesar Colclough (qv) and John Colclough (1767–1807) of Tintern Abbey.