John Costigan (February 1, 1835 – September 29, 1916) was a Canadian judge and politician who served in the House of Commons of Canada and in the Cabinet of several Prime Ministers of Canada. Costigan was born on February 1, 1835, in Saint-Nicolas, Lower Canada, the son of Irish immigrants John Costigan and Bridget Dunn. He was educated at Collège de Sainte-Anne-de-la-Pocatière in Lower Canada from 1850 to 1852. In 1857, he became registrar of deeds and wills for Victoria County in New Brunswick and a judge of the Inferior Court of Common Pleas. He resigned from these posts in 1861 when he was elected to be a member of the 19th New Brunswick Legislative Assembly, representing the electoral district of Victoria.