The Honourable St John Brodrick (c. 1685 – 21 February 1728), was an Irish politician.
Brodrick was son of Alan Brodrick, 1st Viscount Midleton and brother of Alan Brodrick, 2nd Viscount Midleton.
He represented Castlemartyr in the Irish House of Commons from 1709 to 1713, the City of Cork from 1713 to 1715 and then the County of Cork from 1715 to his death. On 9 June 1724 he was appointed to the Irish Privy Council.
By his wife Anne Hill, daughter of Michael Hill of Hillsborough and sister of Trevor Hill, 1st Viscount Hillsborough and Arthur Hill-Trevor, 1st Viscount Dungannon, he had a daughter Anne, who married James Jefferyes of Blarney Castle, son of Sir James Jeffreys and father of James St John Jeffreyes.