There are two species of elephants, African and Asian, and while they are similar in physiology, they are too biologically different to interbreed.
In a further corroboration that African elephants are comprised of two different species (forest and savannah), a new scientific finding discloses that ancient giant elephants living 1.5 million to 100,000 years ago across Eurasia (before eventually becoming extinct) are more closely related to the African forest elephants of today than the forest elephants are related to African savannah elephants! Prior to this finding, most experts agreed that the ancient species of giant elephant was most closely linked to the Asian elephant.