Coordinates: 51°38′24″N 3°22′03″W / 51.640°N 3.3675°W
Ynysybwl (Welsh: Ynys-y-bŵl [ənɪsəˈbʊl]) is a village in Cwm Clydach in Wales. It is situated in the county borough of Rhondda Cynon Taf, roughly 20 miles (32 km) north-north-west of Cardiff, 4 miles (6 km) north of Pontypridd and 10 miles (16 km) south of Merthyr Tydfil, and forms part of the community of Ynysybwl and Coed-y-cwm.
Cwm Clydach is flanked by the Rhondda and Cynon Valleys. The market town of Pontypridd lies to the south at the meeting point of the three valleys; and to the north lies the large Llanwynno forestry. Before the local government reforms of 1996 Ynysybwl was in the Cynon Valley district of Morgannwg Ganol, and the area is historically a part of Glamorgan (Morgannwg).
There is debate over the meaning of the name of the village with several conflicting definitions existing.
Ynys mean island in Welsh but no official translation for bŵl exists. Some theories include mutation from pwll (Welsh for pool), a loan-word from English bowl (a reference to the shape of the valley) or mutation from the name Hywel (a monk from Margam who is said to have worked the land in the 16th Century). Other locally considered meanings of bŵl include rock or coal but neither has any similarity to Welsh equivalent words.