Llanychlwydog 4 stands to the west of the former St David's Church, Llanychlwydog (NPRN 308784).It was first noted in 1883 to the west of the church, and is thought to have been found during the 1864 demolition of the church. When excavated in 1984 had been set into 19th century building rubble. It was removed to Scolton Manor Museum at that time, but was returned to the church before 1992. The stone probably functioned an upright grave marker within the early medieval cemetery excavated within the churchyard. It is one of four early medieval stones found within the churchyard.

The stone is a smooth, quadrangular pillar of microdiorite. Dimensions are given as 132cm height x 63.5 > 56cm width x 28.5 > 21.5cm diameter. It is carved on face A with an outline Latin cross, within which are five plain panels delineated by incised double-outline frames. The carving is thought to date to the ninth to eleventh century.

Sources include:
Edwards, N. 2007, Corpus of Early Medieval Inscribed Stones and Stone Sculpture in Wales

N Vousden, 19 October 2018