Trim Castle is a castle on the south bank of the River Boyne in Trim, County Meath, Ireland, with an area of 30,000 m².
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. The Irish Government currently own and are in charge of the care of the castle, through the state agency The Office of Public Works.
The Office of Public Works operate a Guide Service at Trim Castle and the grounds are open to the public for self-guiding, on payment of an entry fee. Access to the Castle keep is by guided tour only, an entry fee also applies. In winter, the complex is open only on weekends and bank holidays.