Yes, white rhinos (Ceratotherium simum) exist in Tanzania—specifically in the Serengeti National Park, where a reintroduced population of approximately 15,000 thrives (as of recent estimates).
Reintroduced animals are Southern white rhino (C. s. simum) — not the functionally extinct Northern white rhino (C. s. cottoni). Southern whites are Near Threatened (IUCN); ~16,000 wild total, mostly South Africa.
Tanzania also hosts Eastern black rhino (Diceros bicornis michaeli) — critically endangered, ~200 individuals, in Ngorongoro, Serengeti, Mkomazi. Smaller, browser, hooked lip.
Serengeti's white rhino recovery is a rare African conservation success — but sustained funding and political will remain essential.