The name Suthu refers to Basotho people who lived near the source of the river, but were attacked and displaced by the Swazis.

[2] The river rises near Amsterdam, Mpumalanga, South Africa, and flows easterly through Eswatini, where it enters the Lebombo Mountains.

For approximately twenty kilometres, it forms the border between South Africa (province of KwaZulu-Natal) and Mozambique.

[3] In Eswatini, the river is called the Great Usutu or Lusutfu and flows through the towns of Bhunya, Luyengo, Siphofaneni, and Big Bend.

From the origin to its mouth, in order, tributaries are the: Sihanahana, Bonnie Brook, Mpuluzi, Buhlungu, Umvenvane, Lusushwana, Sidvokodvo, Mkhondvo, Mhlamani, Mzimneni, Mzimphofu, Mhlathuzane, Mtsindzekwa, Nyetane, Funuane, and the Pongola Rivers.