The Mara River is a river in that begins in Narok County (Kenya) and in ends in Mara Region (Tanzania), and lies across the migration path of ungulates in the Maasai Mara/Serengeti ecosystem.

Mara Region is one of Tanzania's 31 administrative regions. The region covers an area of 21,760 km2 (8,400 sq mi). The region is comparable in size to the combined land area of the nation state of El Salvador. The neighboring regions are Mwanza Region and Simiyu Region, Arusha Region, and Kagera Region. The Mara Region borders Kenya .The regional capital is the municipality of Musoma. Mara Region is known for being the home of Serengeti National Park, a UNESCO World Heritage site and also the birth place of Tanzania's founding father Julius Nyerere. Under British colonial occupation, the Mara Region was a district called the Lake Province, which became the Lake Region after independence in 1961.