Monasterboice, Christian monastery in County Louth, Ireland.

Monasterboice is a ruined early Christian monastic settlement in County Louth, north of Drogheda. Its graveyard holds the remains of two churches, a round tower about 28 metres tall that lacks its roof, and three 10th-century sandstone high crosses. The crosses carry carved biblical panels; the 5.5-metre Muiredach's High Cross is named in an inscription on its base.

Saint Buithe founded this religious center in the late 5th century as a spiritual community. The site flourished for several centuries until its importance declined after Mellifont Abbey was established in the 12th century.

The crosses are carved in sandstone and belong to Ireland's scriptural group, showing biblical scenes. Muiredach's Cross carries an inscription on its base naming Muiredach as the one who erected it; its panels include Adam and Eve and the Adoration of the Magi. The West Cross, the largest in Ireland at 6.5 m, shows the Baptism of Jesus, David with Goliath's head and Pilate washing his hands.

The site is accessible year-round, allowing visitors to examine the ancient structures and explore the cemetery grounds that remain in use. Most structures are visible, though it helps to walk slowly and allow time for the many details.

The round tower has a preserved entrance positioned about 3.5 meters above ground level that was only reachable by ladder in medieval times. This raised height gave monks a defensive advantage during an era when raids were a constant threat.