Precision measurements of alpha_s with H1 and ZEUS at HERA

Precision measurements of the strong coupling, alpha_s and its
energy-scale dependence performed at HERA by the H1 and ZEUS
collaborations are presented. A HERA average value based on jet
cross-section measurements is also presented. The combined HERA
determinations of alpha_s at various energy scales clearly show the
running of the coupling from these jet data alone and are in agreement
with the prediction of perturbative QCD. The HERA combined alpha_s(M_Z)
value from inclusive-jet cross sections in neutral current deep
inelastic scattering at high Q2 is:
alpha_s(M_Z) = 0.1198 ± 0.0019 (exp.) ± 0.0026 (th.)