Simon John Donnelly, a member of the Irish Republican Army is born at 7 Aungier Street, Dublin, on January 7, 1891. He is a founder member of both Córas na Poblachta and Clann na Poblachta, Irish republican political parties formed in 1940 and 1946 respectively.

Donnelly is the son of Timothy Donnelly, a master plumber, and Mary Brennan. He is the sixth of eight surviving children. The 1911 Census lists him living with his family at 34 Wexford Street. Apprenticed as a plumber, he becomes involved in the Irish Volunteers. During the Easter Rising of 1916 he is the commander of C Company of Éamon de Valera‘s command in Boland’s Mill.

Donnelly is Vice-Commandant of the 3rd Battalion of the Dublin Brigade of the IRA during the Irish War of Independence. On February 10, 1921, he is arrested. Four days later he escapes from Kilmainham Gaol along with Ernie O’Malley and Frank Teeling. Returning to his command in the IRA, he is appointed chief of the Irish Republican Police (IRP) in mid-1921 as part of an attempt to enforce law and order in those areas of the country where the Royal Irish Constabulary (RIC) have been forced out.

Donnelly takes the anti-Treaty side in the Irish Civil War and takes part in the Battle of Dublin (June 28 – July 5, 1922).

Donnelly founds the National Association of the Old IRA in an attempt to mend some of the rifts in the Republican Movement. He is a member of the provisional National Executive of the Republican Prisoners’ Release Association.

On March 2, 1940, Donnelly is one of the founders of Córas na Poblachta and serves as its president. He becomes a founding member of Clann na Poblachta in 1946.

As one of the most senior surviving veterans of the Easter Rising, Donnelly plays a prominent role in the 50th anniversary commemorations in 1966. He dies in Dublin on December 7 of that year.