Physics Gain of a Precise m_t Measurement

The top quark mass is currently measured to delta m_t^{exp,Tevatron} = 2.9 GeV and will be measured at the LHC to a precision of delta m_t^{exp,LHC} \approx 1-2 GeV. We show that even this impressive precision will not be sufficient for many future physics applications. These include electroweak precision observables, Higgs physics in extensions of the Standard Model as well as cold dark matter predictions in Supersymmetry. The desired experimental precision can only be reached at the ILC with delta m_t^{exp,ILC} \approx 100 MeV.