The Province derives its name from the Kasai River which flows through the Kasaï District from south to north.

Kasaï-Occidental borders the provinces of Bandundu to the west, Équateur to the north, Kasai-Oriental to the east, and Katanga to the southeast.

The province is crossed by many major rivers: Kasai, Lulua, Loango, Sankuru, Lukeni, etc...

The province is divided into the Kasaï and Lulua districts, with their headquarters in the towns of Luebo and Tshimbulu.

Tshiluba is used as a first or second language in many towns outside its native area notably in the towns of Luebo, mweka, Ilebo, Kakenge, Luiza, Kamonia, etc... Others natively spoken languages are: The major religion is Christianity, with Catholicism being the largest faith.