Ekegusii is a Bantu language spoken primarily in the Nyanza Province of Kenya by approximately 2.2 million people. There is also a small community of speakers across the border in Tanzania.
From Ethnologue (http://www.ethnologue.com/language/guz):
Alternate Names: Ekegusii, Guzii, Kosova
Population: 2,205,000 in Kenya (2009 census), increasing.
Location: Nyanza Province, Kisii district, south of Kavirondo Gulf. Also in Tanzania (Gusii).
Classification: Niger-Congo, Atlantic-Congo, Volta-Congo, Benue-Congo, Bantoid, Southern, Narrow Bantu, Central, E, Kuria (E.42)
Language Use: 500,000 L2 speakers. Home, community. All ages. Positive attitudes. Also use Kiswahili [swh] and English [eng]. Some may use Egikuria [kuj].
Language Development: Literacy rate in L2: 15%–25%. Taught in primary schools. Dictionary.
Writing: Latin script.
Other Comments: Different from Kisi [kiz] of Tanzania. Kisii is the place name.