Walter de Lacy was lord of Meath in Ireland. He was also a substantial land owner in Weobley, Herefordshire, in Ludlow, Shropshire, in Ewyas Lacy in the Welsh Marches, and several lands in Normandy. He was the eldest son of Hugh de Lacy, a leading Cambro-Norman baron in the Norman invasion of Ireland, and Rohese of Monmouth.

The Lordship of Meath was an extensive seigneurial liberty in medieval Ireland that was awarded to Hugh de Lacy by King Henry II of England by the service of fifty knights and with almost royal authority. The Lordship was roughly co-extensive with the medieval kingdom of Meath. At its greatest extent, it included all of the modern counties of Fingal, Meath, Westmeath as well as parts of counties Cavan, Kildare, Longford, Louth and Offaly. The Lordship or fiefdom was imbued with privileges enjoyed in no other Irish liberty, including the four royal pleas of arson, forestalling, rape, and treasure trove.