Patrick James Smyth (c. 1823 – 1885) also known as Nicaragua Smyth, was an Irish politician and journalist.
He was educated at Clongowes Wood College where he became friends with Thomas Francis Meagher, with whom he joined the Repeal Association in 1844. Following his involvement in the Young Irelander Rebellion of 1848, Smyth fled to America where he worked as a journalist and became involved in the New York Irish Directory. There he was persuaded to go to Van Diemen's Land (now Tasmania) in 1853 to facilitate the escape to America of John Mitchel, the Irish activist. Whilst there he married a local girl Jeannie Regan. Smyth was nicknamed Nicaragua by Mitchel on account of the former's support for railway projects in that country.
On his return to Ireland Smyth was elected a Home Rule Party Member of Parliament (MP) for Westmeath at a by-election on 17 June 1871, and was reelected in 1874. At the 1880 general election, he did not seek re-election in Westmeath, but stood instead in Tipperary, where he was elected unopposed. He left the House of Commons at the end of 1884, when he was appointed as Secretary to the Irish Loan Fund Board.
In 1871 he was made chevalier of the Légion d'honneur.