The name Dwygyfylchi is derived from the Welsh dwy, "two", and cyfylchi, a word used almost exclusively in placenames meaning a "circular fortress"; it was first recorded as "Dwykyvelchy" in 1287.

[citation needed] Approximately half of Dwygyfylchi forms the most northern tip of the Snowdonia National Park.

To the west the larger headland of Penmaenmawr divides them from the town of Llanfairfechan and the wider coastal plain extending to Bangor.

To the south an arc of hills and uplands extends east to west from the latter to Penmaen Mawr, beginning with Yr Allt Wen above Dwygyfylchi, Bwlch Sychnant (the old road crosses this pass to Conwy) and Pen-sychnant at Capelulo.

The rounded hill of Foel Lys, Gwddw Glas (Green Gorge), Bryn Derwydd and the head of Cwm Graiglwyd and finally Penmaenmawr itself.

The coastal plain itself is nearly divided by Trwyn-yr-Wylfa, which also marks the boundary between the "Hen Bentra" or "Old Village" of Dwygyfylchi and Capelulo in the east and Pant-yr-afon and Penmaenan in the west .

The first and larger, Afon Gyrrach, runs for about 4 miles (6.4 km) from the northern slopes of Tal-y-Fan to the sea near Penmaenbach, passing through Nant Ddaear-y-llwynog ("Fairy Glen") and the old villages of Dwygyfylchi and Capelulo.

The legend states the remains of Llys Helig, said to be his palace, can be seen at exceptionally low tides, this being near the Conwy channel, about a mile or so off the coast at Penmaenmawr.

Dwygyfylchi is also associated with Saint Ulo, Capelulo at the foot of Sychnant reputedly having been the site of an early medieval church.

Dwygyfylchi lies on the route of the A55 Expressway providing access at Junction 16 and at 16A to Penmaenmawr to and from the rest of the north coast.