A measurement of direct photon production in Pb-208 + Pb-208 collisions at
158A GeV has been carried out in the CERN WA98 experiment. The invariant yi
eld of direct photons in central collisions is extracted as a function of t
ransverse momentum in the interval 0.5 < p(T) < 4 GeV/c. A significant dire
ct photon signal, compared to statistical and systematical errors, is seen
at p(T) > 1.5 GeV/c. The result constitutes the first observation of direct
photons in ultrarelativistic heavy-ion collisions. It could be significant
for diagnosis;of quark-gluon-plasma formation.