Born Lord Francis Almeric Spencer, he was the second youngest of the 4th Duke of Marlborough,[1] and his wife, Lady Caroline Russell.

[1] From 1801 to 1815, he was Member of Parliament (MP) for Oxfordshire and on his retirement from the Commons, was raised to the peerage as Baron Churchill, of Wychwood in the County of Oxford.

[2] During the Napoleonic Wars he raised a Troop of volunteer cavalry in Oxford and was appointed its Captain on 3 November 1803[3] After the wars the independent troops in the county were consolidated into the North Western Oxfordshire Regiment of Yeomanry, with Spencer (now Lord Churchill) as Lieutenant-Colonel.

William Henry Spencer, married Elizabeth Rose Thornhill in January 1838.

Mount Churchill in British Columbia, Canada, was named in his honor in 1860 by Sir George Henry Richards.