Lead–vacancy (PbV) centers in diamond are promising candidates for terahertz (THz) sensing owing to their large ground-state splitting induced by strong spin–orbit coupling. Here, we combine first-principle calculations and spectroscopy to investigate their structural and optical properties. Constrained-occupation density functional theory (CDFT) predicts a zero-phonon line (ZPL) at ~ 539 nm and a zero-field splitting (ZFS) of ~ 4.6 THz. Guided by these results, we fabricated PbV centres via ion implantation and high-temperature annealing, and developed a low-temperature spectroscopic platform for optical characterization. Experiments reveal a ZPL at 552–558 nm with an energy separation of ~ 3.3–5.8 THz, in close agreement with theory. These findings confirm that PbV centres exhibit THz-scale ground-state splitting, highlighting their potential for next-generation nanoscale THz sensors.