Hayes St Leger, 4th Viscount Doneraile

Hayes St Leger, 4th Viscount Doneraile (1 October 1818 – 26 August 1887) was a member of the Peerage of Ireland who was an Irish representative peer in the British House of Lords between 1855 and his death.

Family Doneraile was the son of Hayes St Leger, 3rd Viscount Doneraile and Lady Charlotte Esther Bernard. He married Mary Ann Grace Louisa Lenox-Conyngham, the daughter of George Lenox-Conyngham and Elizabeth Holmes, on 20 August 1851. He was a Conservative and a member of the Carlton Club. Rarely present in Parliament, he voted by proxy for the Earl of Derby's 1857 resolution condemning the conduct of the Second Opium War. He was High Sheriff of County Cork for 1845, a Deputy Lieutenant for County Cork, and was the Honorary Colonel of the North Cork Rifles militia regiment (later the 9th Battalion, King's Royal Rifle Corps) from 25 November 1874. Doneraile was a prominent and frequent fox hunter, and was Master of Fox Hounds at the Burton Hunt in Lincolnshire and President of the Duhallow Hunt in Mallow. While Barrer survived, Doneraile began to feel unwell on 22 August and to suffer convulsions and delirium on 25 August, dying the following morning at home in Doneraile Court. The relatively late and mild onset of symptoms was attributed at the time to the partial effect of the vaccine. The death of such a notable fed the controversy over the vaccine. Victor Horsley said Doneraile "refused to go through the treatment ordered"; later accounts suggest Doneraile cut short his treatment through boredom or impatience.