The Pahang River is a river that mainly flows through the state of Pahang, Malaysia. Its drainage basin covers its namesake state as well as the neighbouring state of Negeri Sembilan.

Pahang, officially Pahang Darul Makmur with the Arabic honorific Darul Makmur is a sultanate and a federal state of Malaysia. It is the third largest state in the country and the largest state in Peninsular Malaysia by area, and ninth largest by population. The state occupies the basin of the Pahang River, and a stretch of the east coast as far south as Endau. Geographically located in the East Coast region of the Peninsular Malaysia, the state shares borders with the Malaysian states of Kelantan and Terengganu to the north, Perak, Selangor and Negeri Sembilan to the west, Johor to the south, while South China Sea is to the east. The Titiwangsa mountain range that forms a natural divider between the peninsula's east and west coasts is spread along the north and south of the state, peaking at Mount Tahan, which is 2,187 metres (7,175 ft) high. Although two thirds of the state is covered by dense rain forest, its central plains are intersected by numerous rivers, and along the coast there is a 32-kilometre (20 mi) wide expanse of alluvial soil that includes the deltas and estuarine plains of the Kuantan, Pahang, Rompin, Endau, and Mersing rivers.