Nepean River is a major river in eastern New South Wales, Australia. Its main tributaries include the Avon, Cataract, and Cordeaux rivers. The Nepean and its tributaries have reservoirs that provide water for the city of Sydney. Farmers in lands drained by the Nepean raise livestock and grow vegetables for Sydney markets. 
The Nepean River rises in the Illawarra Range east of Bowral. It travels generally north until it meets the Grose River at the Yarramundi nature reserve, just west of Windsor. At that junction, the Nepean and Grose merge into the Hawkesbury River. Together, the Hawkesbury and Nepean form one of the largest river systems in New South Wales. The Hawkesbury-Nepean ecosystem supports a diversity of native wildlife, including the platypus and the Australian bass, a kind of freshwater fish.
The Nepean River is known as the Yandhai to the area’s traditional inhabitants, the Darug Aboriginal people. In the Darug language, Yandhai means walking in past or present. In 1788, an expedition led by the British explorer Watkin Tench encountered the river. At that time, New South Wales was a British colony. Tench informed Arthur Phillip, the colony’s British governor, about his discovery. Phillip named the river in honor of his friend Evan Nepean, undersecretary of state in the British Home Department.
During the mid-1800’s, floods destroyed a number of bridges that had been built across the Nepean River. Victoria Bridge, an iron railway bridge across the Nepean, opened to commercial traffic in 1867. That same year, the region experienced one of its worst floods. The Nepean overflowed into nearby communities, and floodwaters covered large parts of Penrith. Victoria Bridge survived the flood but was closed for repairs. It reopened in 1869. In the early 1900’s, a second railway bridge across the Nepean was built near Victoria Bridge. A pedestrian bridge opened in 2018. It connected the communities of Emu Plains and Penrith, on opposite sides of the river.
