Histone H3-like variant which exclusively replaces conventional H3 in the nucleosome core of centromeric chromatin at the inner plate of the kinetochore. Required for recruitment and assembly of kinetochore proteins, mitotic progression and chromosome segregation. May serve as an epigenetic mark that propagates centromere identity through replication and cell division (By similarity). Forms a nucleosome-like histone octamer containing two molecules each of H2A, H2B, CENH3 and H4 assembled in one CENH3-H4 heterotetramer and two H2A-H2B heterodimers (By similarity). Interacts with ORTH2. Localizes exclusively in the kinetochore domain of centromeres (PubMed:12034896, PubMed:17028205). Localized at centromeres in both mitotic and meiotic cells (PubMed:21695238). Expressed and/or deposited to centromeres during G2 phase. The C-terminal histone fold domain is sufficient to direct CENH3 to centromeres. Belongs to the histone H3 family.