King John's Castle
King John's Castle may refer to:
- King John's Castle (Limerick), Limerick City, Ireland
 - King John's Castle (Carlingford), County Louth, Ireland
 - King John's Castle (Kilmallock), County Limerick, Ireland
 - King John's Castle in Kineton, Warwickshire, United Kingdom
 - King John's Castle, a horse that finished second in the 2008 Grand National
 
See also
- Athenry, County Galway
 - Naas, County Kildare
 - Odiham Castle near Odiham, Hampshire
 - Trim Castle, County Meath