Former Owner
- John Josias Conybeare1
- John Lee1
- John Lumley, 1st Baron Lumley1
- John McRay1
- John Morley1
- John Pery1
- John Roland Abbey1
- John Rolls, 1st Baron Llangattock1
- John Ruskin1
- John Shirley1
- John Sidney Hawkins1
- Joseph Jekyll1
- Juan de Gayferos de Eguiraum1
- Justin MacCarthy Reagh1
- Laurence Kirby1
- Laurence Vaux1
- Leonello d'Este, Marquis of Ferrara1
- Llewelyn Lloyd-Mostyn, 3rd Baron Mostyn of Mostyn1
- Long Island Historical Society, Maine1
- Louis Loewe1