The inclusive cross section for top-quark pair production measured by the CMS experiment in proton–proton collisions at a center-of-mass energy of 7TeV is compared to the QCD prediction at next-to-next-to-leading order with various parton distribution functions to determine the top-quark pole mass, m_t^pole,or the strong coupling constant, α_S. With the parton distribution function set NNPDF2.3, a pole mass of 176.7_−3.4^+3.8 GeV is obtained when constrainingαS at the scale of the Z boson mass, m_Z, to the current world average. Alternatively, by constraining m_t^pole to the latest average from direct mass measurements, a value of α_S(m_Z)=0.1151_−0.0032 ^+0.0033is extracted. This is the first determination of α_S using events from top-quark production.