The Riverina (/ˌrɪvəˈriːnə/) is an agricultural region of south-western New South Wales, Australia. The Riverina is distinguished from other Australian regions by the combination of flat plains, a climate with significant seasonal variation and an ample supply of water for irrigation. This combination has allowed the Riverina to develop into one of the most productive and agriculturally diverse areas of Australia. Bordered on the south by the state of Victoria and on the east by the Great Dividing Range, the Riverina covers those areas of New South Wales in the Murray and Murrumbidgee drainage zones to their confluence in the west.

Home to Aboriginal groups including the Wiradjuri people for over 40,000 years, the Riverina was colonised by Europeans in the mid-19th century as a pastoral region providing beef and wool to markets in Australia and beyond. In the 20th century, the development of major irrigation areas in the Murray and Murrumbidgee valleys has led to the introduction of crops such as rice and wine grapes. The Riverina has strong cultural ties to Victoria, and the region was the source of much of the impetus behind the federation of Australian colonies.

Major population and service centres in the Riverina include the cities of Wagga Wagga, Leeton, Griffith and Albury. Wagga Wagga is home to a campus of Charles Sturt University and two major Australian Defence Force establishments. La Trobe University has a campus in Albury–Wodonga, located just across the state border in Wodonga, Victoria.

The delineation of the Riverina region varies by government agency or body. Common official boundaries include the Australian Bureau of Statistics' Statistical Area Level 4 Riverina region, Australian Electoral Commission's Federal Election Boundary called Riverina, Natural Resource Management Regions Riverina region, Regional Development Australia's Riverina region and Interim Biogeographic Regionalisation for Australia's Riverina region.

In common usage the Riverina generally comprises the agricultural and pastoral areas of New South Wales, west of the Great Dividing Range and in the drainage basin of the snow-fed Murray and Murrumbidgee Rivers. The northern boundary beyond the Riverina is determined by the Lachlan River catchment area and is referred to as the Central West. Along the Murray to the south, the Riverina borders the state of Victoria. West of the confluence of the Murray and Murrumbidgee is the beginning of the more arid Far West region.

In general, the Riverina is an alluvial plain formed by deposition carried from the Great Dividing Range by streams between 30,000 and 15,000 years ago. The terrain includes rolling hills to the east but then becomes flatter to the west with most of that plain reaching less than 200 metres (660 ft) above sea level. The western Riverina consists largely of featureless saltbush plain.

The geology of the Riverina comprises several troughs and sedimentary basins. The western Riverina is presumed to be a continuation of the Ballarat and Bendigo geological zone while eastern sections are underlain by western portions of the Lachlan Fold Belt. There is potential for the Riverina to host several mineral deposit types including coal, petroleum, coal seam methane, gypsum, orogenic gold, Cobar style polymetallic systems, heavy mineral sands and possibly diamonds in these fold belt rocks and basins. Riverina soils are generally sandy along the river channels, with more saline grey and brown clays found on rarely flooded areas on the perimeter of the floodplain. As the Murrumbidgee passes downstream, the water and soil become more saline.

The Riverina is drained by the large Murray-Darling Basin. Rivers and streams in the Riverina generally flow east to west. As well as the Murray, Murrumbidgee and Lachlan, other streams include Billabong Creek and the Edward River, an anabranch of the Murray. Much of the water carried by these streams is diverted. In 2001–2002, 52% of the Murray and Murrumbidgee water runoff was diverted, 77% of which was used for irrigation.