The Msunduzi River, also known as the Dusi River (its anglicised name, derived from the isiZulu "Msunduzi"), flows through the centre of Pietermaritzburg, the provincial capital of KwaZulu-Natal, South Africa. It is a tributary of the Mngeni River, joining it downstream before the Mngeni continues to Durban and the Indian Ocean. The river gives its name to the Msunduzi Municipality in which Pietermaritzburg is located.

Within Pietermaritzburg, a portion of the river has been dammed by weirs to create the Camps Drift section, a flat-water stretch historically used for canoe and rowing practice. This section has served as the traditional starting point of the Dusi Canoe Marathon, though in recent years the race start has been relocated to Bishopstowe Hall due to dangerously elevated E. coli levels at Camps Drift.

The river is most widely known as the starting stretch of the Dusi Canoe Marathon, an annual three-day race covering approximately 120 kilometres from Pietermaritzburg to Durban along the Msunduzi and Mngeni Rivers. Founded in 1951 by Ian Player, it is considered the largest canoeing event on the African continent and attracts around 2,000 paddlers in strong years. The race alternates annually between K1 (single) and K2 (double) boat formats, though both options are available each year. The course involves rapids, technical portages, and significant physical demands over three days, with two overnight stops along the route.

Water quality is a serious and well-documented concern on the Msunduzi. The river is regarded as one of the most polluted in the region, with primary contaminants including raw sewage, chemical and organic waste, and solid waste discharged continuously into the river. These conditions have led to widespread illness among paddlers — in one recent Dusi event, over 60% of participants reported gastrointestinal illness of varying severity. The degraded state of the Msunduzi also affects the larger Mngeni River downstream, which serves as a drinking water source for Pietermaritzburg, Durban, and surrounding towns. Paddlers should treat water quality as a significant health hazard and take appropriate precautions regarding skin exposure and accidental ingestion.