Carnedd Llewelyn, also spelled Carnedd Llywelyn, is a mountain massif in the Carneddau range in Snowdonia, north-west Wales. It is the highest point of the Carneddau and the second highest peak by relative height in Wales, 49th in the British Isles and lies on the border between Gwynedd and Conwy.

The Carneddau are a group of mountains in Snowdonia, Wales. They include the largest contiguous areas of high ground in Wales and England, as well as six or seven of the highest peaks in the country—the Fifteen Peaks. The range also encloses a number of lakes such as Llyn Cowlyd and Llyn Eigiau, and the Aber Falls waterfall. It is delimited by the Irish Sea to the north, the Conwy valley to the east, and by the A5 road from Betws-y-Coed to Bethesda to the south and west. The area covers nearly 200 square kilometres (80 sq mi), about 10% of the area of Snowdonia. The area is bordered by three main roads—the A55, the A5 to the south and the A470 to the east.