Merriwa River, a perennial river of the Hunter River catchment, is located in the Upper Hunter region of New South Wales, Australia.

Merriwa River rises on the southern slopes of the Great Dividing Range, below Oxleys Peak, north of Merriwa and flows generally south, joined by eight minor tributaries before reaching its confluence with the Goulburn River below Mount Kerrabee. The river descends 317 metres (1,040 ft) over its 78 kilometres (48 mi) course.

At the town of Merriwa, the Golden Highway crosses the Merriwa River.

Merriwa is thought to be derived from the Aboriginal word meaning "grass seeds."

• Rivers of New South Wales
• List of rivers of New South Wales (L–Z)
• List of rivers of Australia
• Goulburn River National Park

• "Hunter River catchment" (map). Office of Environment and Heritage. Government of New South Wales.
• Merriwa online community website

32°06′S 150°22′E / 32.100°S 150.367°E / -32.100; 150.367