Tin-vacancy (Sn-V) color centers were created in diamond via ion implantation and subsequent high-temperature annealing up to 2100 °C at 7.7 GPa. The first-principles calculation suggested that a large atom of tin can be incorporated into a diamond lattice with a split-vacancy configuration, in which a tin atom sits on an interstitial site with two neighboring vacancies. The Sn-V center showed a sharp zero phonon line at 619 nm at room temperature. This line split into four peaks at cryogenic temperatures, with a larger ground state splitting (∼850 GHz) than that of color centers based on other group-IV elements, i.e., silicon-vacancy (Si-V) and germanium-vacancy (Ge-V) centers. The excited state lifetime was estimated, via Hanbury Brown-Twiss interferometry measurements on single Sn-V quantum emitters, to be ∼5 ns. The order of the experimentally obtained optical transition energies, compared with those of Si-V and Ge-V centers, was in good agreement with the theoretical calculations.