With an area of 1510 kmē the Masai Mara is not the largest game park in Kenya, but it is probably the most famous. The entire area of the park is nestled within the enormous Great Rift Valley that extends from the Mediterranean Sea to South Africa. The terrain of the reserve is primarily open grassland, with seasonal riverlets. In the south-east region are clups of the distinctive acacia tree.

The Masai Mara is perhaps most famous for its lions. All other members of the "Big Five" are to be found in the Masai Mara.
As in the Serengeti, the wildebeest are the dominant inhabitant of the Masai Mara, and their numbers are estimated in the millions. Around July of each year these ungainly animals migrate in a vast ensemble north from the Serengeti plains in search of fresh pasture, and return to the south around October. The Great Migration is one of the most impressive natural events worldwide, involving an immensity of herbivores: some 1,300,000 Wildebeest, 360,000 Thompson Gazelle, and 191,000 Zebra. These numerous migrants are followed along their annual, circular route by a block of hungry predators, most notably lions and hyena.

Numerous other antelope can be found, including Thompson and Grant's gazelle, impala, topi and Coke's hartebeest. Large herds of zebra are found through the reserve. The plains are also home to the distinctive Masai Giraffe as well as the common giraffe.