John Ignatius Milroy, known as Seán Milroy (1877 – 30 November 1946), was an Irish revolutionary and politician, who took part in the 1916 Easter Rising and served in the Second Dáil during the War of Independence and in the Senate of the Irish Free State.
Milroy was born in Maryport, Cumbria, England. He was a journalist by profession.
He was a close personal friend of Arthur Griffith and an early member of Sinn Féin, serving on its national executive from 1909 to 1912. He joined the Irish Volunteers, and in 1915 he was arrested and imprisoned for three months for a speech in which he urged Irishmen not to fight in the First World War. He fought in the Easter Rising in 1916, and was imprisoned in England.
Milroy contested a by-election for Sinn Féin in Tyrone North East unsuccessfully. He was elected a Sinn Féin Teachta Dála (TD) at the 1921 elections for both the Cavan constituency and for the Fermanagh and Tyrone constituency. He supported the Anglo-Irish Treaty and voted in favour of it.
He became a member of Cumann na nGaedheal but left the party in 1924 along with seven other TDs in opposition to the Government's actions to the so-called Irish Army mutiny. He contested the June 1927 general election unsuccessfully.