Trim Castle (Irish: Caisleán Bhaile Atha Troim) is a Norman castle on the south bank of the River Boyne in Trim, County Meath, Ireland. With an area of 30,000 m², it is the largest Norman castle in Ireland. Over a period of 30 years, it was built by Hugh de Lacy and his son Walter as the caput of the Lordship of Meath.