Undercoordination-induced slight bond contraction of the pristine edge is a conventional edge self-reconstructed pattern in two-dimensional materials that generally cannot drive the edge into its ground state. Despite reports of unconventional edge self-reconstructed patterns of 1H-phase transition metal dichalcogenides (TMDCs), there have been no reports of sister 1T-phase TMDCs. Here, we predict an unconventional (2 × 1) edge self-reconstructed pattern for 1T-TMDCs by considering 1T-TiTe 2 . A novel self-reconstructed trimer-like metal zigzag edge (TMZ edge) with one-dimensional metal atomic chains and Ti 3 trimers is uncovered. Its metal triatomic 3d orbital coupling leads to Ti 3 trimerization. This TMZ edge occurs in group IV, V, and X 1T-TMDCs and has an energetic advantage far beyond conventional bond contraction. The unique triatomic synergistic effect results in better catalysis of the hydrogen evolution reaction (HER) for the 1T-TMDCs than with commercial platinum-based catalysts. This study provides a new strategy for maximizing the HER catalytic efficiency of 1T-TMDCs by using atomic edge engineering.