We study the impact of electroweak radiative corrections on direct
production of photons with high transverse momenta at hadron colliders.
Analytic results for the weak one-loop corrections to the parton
scattering reaction $\bar q q \to \gamma g$ and its crossed variants are
presented. For the high-energy region, where the corrections are strongly
enhanced by logarithms of $\hat s/M_W^2$, we derive simple asymptotic
expressions which approximate the exact one-loop results with high
precision. The dominant two-loop electroweak contributions are also
calculated. Numerical results are presented for the LHC and the Tevatron.
The corrections are negative and their size increases with transverse
momentum. For the LHC, where transverse momenta of 2 TeV or more can be
reached, the size of the one- and two-loop effects amounts up to -17\% and
+3\%, respectively. At the Tevatron, with transverse momenta up to 400
GeV, the one-loop corrections do not exceed -4\% and the two-loop effects
are negligible. Finally we compare the cross sections for hadronic
production of photons and Z bosons and find that the electroweak
corrections have an important impact on their ratio.