The hydrogen evolution reaction (HER) is crucially important for water splitting, for which platinum (Pt) has been considered the state-of-the-art electrocatalyst. Despite recent progress in non-Pt electrocatalysts, few Pt-free catalysts can compete against Pt in terms of HER activity particularly in alkaline solution. Here, we report a new efficient Pt-free HER catalyst – hybrid ruthenium cobalt phosphide (RuCoP) cluster where Ru exists in metallic chemical state in the hybrid. The unique hybridization allows electron transfer to take place from both Co and P to Ru, thereby significantly enhancing the hybrid’s HER activity. The as-synthesized RuCoP clusters demonstrate a considerably low overpotential (η) of 11 mV at -10 mA cm² and a high turnover frequency (TOF) of 5.64 s^-1 at η = 100 mV in 0.5 M H₂SO₄. Remarkably, even in alkaline solution (1.0 M KOH) the excellent HER performance of RuCoP remains, with a very low η₁₀ of 23 mV and exceptionally high TOF value of 3.85 s^-1 at η = 100 mV. Moreover, the RuCoP catalysts show outstanding catalytic stability toward the HER in both acidic and alkaline solutions, superior to that of commercially available Pt/C catalysts.