  We summarize the current top-quark mass measurements from the CDF and D0
experiments at Fermilab. We combine published Run I (1992--1996) results with
the most precise published and preliminary Run II (2001--2011) measurements
based on data corresponding to up to 9.7 fb$^{-1}$ of $p\bar{p}$ collisions.
Taking correlations of uncertainties into account, and combining the
statistical and systematic uncertainties, the resulting preliminary Tevatron
average mass of the top quark is $M_{top} = 174.34 \pm 0.64 ~GeV/c^2$,
corresponding to a relative precision of 0.37%.
