Llandyrnog sits in the Vale of Clwyd roughly midway between Denbigh and Ruthin, in the valley of the River Clwyd. The wider area around the village was historically divided between several small medieval ecclesiastical parishes — Llandyrnog, Llangwyfan, Llangynhafal and Llanychan, alongside the larger parish of Llanynys — a patchwork that reflects a long history of small, scattered rural communities rather than a single dominant settlement.
Early archaeological finds in the surrounding area, including a Neolithic polished flint axe near Llangwyfan church and a Bronze Age arrowhead near Gellifor, point to settlement here stretching back thousands of years, likely connected to a wider network of lookout and refuge sites used to watch for approaching danger and shelter livestock in troubled times.
Administratively the village has moved between counties more than once in recent history: it fell within the old deanery of Llanfair Dyffryn Clwyd until that was transferred to the diocese of St Asaph in 1859, and was later part of the short-lived county of Clwyd between 1974 and 1996, before Denbighshire was re-established in its modern form.
Llandyrnog is a rural village at the foot of the Clwydian Range, its name referring to the local church dedicated to the Celtic saint Tyrnog. The surrounding farmland is some of the most productive in the Vale of Clwyd, and the village has traditionally served as a local hub for the agricultural communities scattered across the eastern side of the valley.
The village sits within easy reach of several of the Clwydian Range's hillforts and walking routes, making it a useful, quieter base for visitors who want to explore the hills without staying in a larger town, and its parish church retains features of interest for those tracing the religious history of the valley.