MacCarthy, Sir Charles (1764–1824), soldier and abolitionist, was born in Cork city, second son of Jean Gabriel Guéroult, a royal official of Nogent-le-Rotrou in France, and Charlotte Michelle Guéroult (née MacCarthy). His uncle, Capt. Thaddeus MacCarthy, an officer in the guards of Louis XV, persuaded him when still young to adopt his mother's maiden name. He was commissioned as a sous-lieutenant in the French army in 1785, serving with Berwick's Regiment of the Irish Brigade. Promoted to captain (August 1791), he served with the French émigré army at Koblenz, under the command of the prince de Condé, and was wounded at the battle of the Canal de Louvain (15 July 1794). He then served with the duc de Castries’ regiment in the émigré army but, after the collapse of the royalist cause, entered the British service as an ensign of the 5th Regiment of the Irish Brigade on 1 October 1794. He served in the West Indies and was later promoted to lieutenant (31 December 1795) and captain (1 October 1796). While returning from Honduras in June 1798 on the transport ship Calypso, he helped defend the ship in an engagement with a French privateer and was badly wounded in the right arm, a musket ball passing through the elbow. After further service with the West India Regiment, he transferred into the 52nd Foot in 1800.
In April 1804 he was promoted to major and went to New Brunswick to take command of the New Brunswick Fencibles. Promoted to lieutenant-colonel (May 1811), he travelled to the west coast of Africa to take up an appointment with the Royal African Corps. In 1812 he was appointed as governor of Senegal and Goree. When these settlements were returned to the French after the treaty of 1814, he was appointed as governor of Sierra Leone. MacCarthy was a noted abolitionist and had made known his feelings regarding slavery when he was serving in the West Indies. He rigorously enforced the anti-slavery laws in West Africa, founded villages for liberated slaves, and built churches and schools. He also actively supported the work of the Church Missionary Society. In November 1820 he was knighted, and in 1821 he was promoted to full colonel and appointed brigadier-general commanding British forces in West Africa. When the African Company of Merchants was abolished in 1821 (primarily due to their refusal to enforce the anti-slavery laws), he assumed the governorship of their possessions on the Gold Coast.
In late 1823 news was received that the army of the Ashanti king, around 20,000 strong, was marching towards the Cape Coast to attack British settlements. This was due to a gradual breakdown in relations between the British administration and the Ashantis, and dated back to the Ashanti victory of 1816 over their neighbours, the Fantis. Yet it was also known that the Ashanti kingdom was rich in gold, and the Ashanti–British war of 1823–31 marked the beginning of a series of attempts to establish a British protectorate, a scheme finally realised in 1897. Numerous attempts at diplomacy over the previous months had failed to pacify the Ashanti king, and MacCarthy had to organise the defence of the British settlement. On 10 January 1824 he set out with a force of around 500 men to meet the Ashanti army, which he engaged on 21 January on the banks of the Adumansu, a tributary of the River Pra, and initially put up a spirited defence. When his troops ran out of ammunition, the position was overrun and MacCarthy was wounded in the arm and the chest. Despite the efforts of his officers to defend him, he was surrounded by Ashantis and beheaded, his head reportedly being taken as a trophy.
He married (1812) Antoinette Carpot; they had one son, Charles. After the death of his father, the young Charles MacCarthy was adopted by his uncle, the comte de Mervé, and later succeeded to that title.