Thomas Stanislaus MacDonagh was an Irish political activist, poet, playwright, educationalist and revolutionary leader. He was one of the seven leaders of the Easter Rising of 1916, a signatory of the Proclamation of the Irish Republic and Commandant of the 2nd Battalion, Dublin Brigade of the Irish Volunteers, which fought in Jacob's biscuit factory. He was executed for his part in the Rising at the age of thirty-eight.

The Proclamation of the Republic, also known as the 1916 Proclamation or the Easter Proclamation, was a document issued by the Irish Volunteers and the Irish Citizen Army during the Easter Rising in Ireland, which began on 24 April 1916. In it, the Military Council of the Irish Republican Brotherhood, writing as the "Provisional Government of the Irish Republic," proclaimed Ireland's independence from the United Kingdom. The reading of the proclamation by Patrick Pearse outside the General Post Office (GPO) on Sackville Street, Dublin's main thoroughfare, marked the beginning of the Rising. The proclamation was modelled on a similar independence proclamation issued during the 1803 rebellion by Robert Emmet.