Rhidian was a 6th-century Welsh Pre-congregational Saint who is often associated with St Illtyd.Churches and Religious Places in Glamorgan.
Rhydian might be a corruption of 'Tryrulhid’, who was St Illtyd's wife. However, there are also legends about a male Celtic monk,Yr Eglwys yng Ngogledd Gŵyr.St. Rhidian & St. Illtyd Church, Llanrhidian. by this name, who went on pilgrimage to St Davids.
Rhidian is the patron saint of Llanrhidian in Wales.
References
fr:Saint Therezien