he is a Vepsian.
Yeah.... already covered here:
i only know that he is a Vepsian.
He is multi-ethnic, with mixed Russian, Vepsian and Karelian ancestry. But since he became active in the politics, he has tried to hide his non-Russian ancestry. His great-grandparents had the surname Putiaynen, which they changed to Putin after Russification. Once Putin was asked some media person whether he considers himself as a Vepsian or Karelian. Putin carefully avoided answering that.
BTW... I don't think that the Russians care much about his ethnic origin. Even his predecessor (Boris Yeltsin) was not 100% ethnic Russian. He was rumored to have some Vogul (Mansi) ancestry.