  We present a measurement of the electric charge of top quarks using
$t\bar{t}$ events produced in $p\bar{p}$ collisions at the Tevatron. The
analysis is based on fully reconstructed $t\bar{t}$ pairs in lepton+jets final
states. Using data corresponding to 5.3 $\rm fb^{-1}$ of integrated luminosity,
we exclude the hypothesis that the top quark has a charge of $Q=-4/3\,e$ at a
significance greater than 5 standard deviations. We also place an upper limit
of 0.46 on the fraction of such quarks that can be present in an admixture with
the standard model top quarks ($Q=+2/3\,e$) at a 95\% confidence level.
