Lord Henry FitzGerald, PC (Ire), diplomat, soldier, and younger brother of revolutionary Lord Edward FitzGerald, is born on July 30, 1761. He is the fourth son among nine sons and ten daughters of James FitzGerald, 1st Duke of Leinster, and Emily FitzGerald, Duchess of Leinster (née Lady Emily Lennox).

FitzGerald joins the British Army and becomes a lieutenant in the 66th (Berkshire) Regiment of Foot in 1788, transferring as a captain in 1779 to the newly raised 85th Regiment of Foot (Westminster Volunteers), which is posted to garrison duty in Jamaica for the duration of the American Revolutionary War. He is there promoted to major in 1781 and lieutenant colonel in 1783, taking over command of the regiment from General Charles Stanhope, 3rd Earl of Harrington. After the 85th is disbanded in 1783 he becomes a captain and lieutenant colonel in the 2nd Foot Guards in 1789 and retires from active service in 1792.

FitzGerald is a Member of Parliament (MP) for Kildare Borough between 1783 and 1790 and represents Athy between 1790 and 1791. From 1790 to 1798, he sits in the Irish House of Commons for Dublin City. On July 8, 1806, he is appointed to the Privy Council of Ireland, and from 1807 until 1814, he serves in the Parliament of the United Kingdom for Kildare. He also holds the position of one of the joint Postmasters General of Ireland from April 1806 until May 1807.

FitzGerald is a member of the Kildare Street Club in Dublin. He dies at Boyle Farm, Thames Ditton, Surrey, England, on July 9, 1829. He is buried at St. Mary’s Paddington Green Churchyard, Paddington, City of Westminster, Greater London, England

FitzGerald marries Charlotte Boyle Walsingham in London on August 3, 1791. Together they live at Boyle Farm, Thames Ditton. In 1806, his wife succeeds to the Baron de Ros, the premier baron in the Peerage of England, as 20th Baroness de Ros. The family then takes the surname FitzGerald-de Ros. The couple has 13 children in 21 years, of which nine survive to adulthood.