Former Owner
- Joannes Salzperg1
- Johann Egolph1
- Johann Heinrich von Speyr-Passavant1
- Johann von Firmian1
- John Alexander Stewart1
- John C. Jackson1
- John Eliot Hodgkin1
- John Fenn1
- John Frederick Lewis1
- John Towneley1
- Joseph Anton Koch1
- Joseph Ernst Koch-Sternfeld1
- Joseph Halle Schaffner1
- Juan Antonio de la Reguera1
- Juan Burgueño1
- Juan de Gayferos de Eguiraum1
- Juana I of Castile1
- Julian Burgueño1
- Karl Hermann Berendt1
- Katherine Somerset Wyttenbach Fenwick1