We prove basic theorems about the ground states of the S = 1 Bose-Hubbard model. The results are quite universal and depend only on the coefficient U-2 of the spin-dependent interaction. We show that the ground state exhibits saturated ferromagnetism if U-2 < 0, is spin-singlet if U-2 > 0, and exhibits "SU(3)-ferromagnetism" if U-2 = 0, and completely determine the degeneracy in each region. DOI: 10.1103/PhysRevLett.110.130405