Precision Higgs boson mass determination at lepton colliders

We demonstrate that a measurement of the Bjorken process $e^+e^-, \mu^+\mu^-\to ZH$ in the threshold region can yield a precise determination of the Higgs boson mass. With an integrated luminosity of $100 fb^{-1}$, it is possible to measure the Higgs mass to within 60 MeV (100 MeV) for m_H=100 GeV (150 GeV).