  We report the results of Swift observations of the Gamma Ray Burst GRB
050603. With a V magnitude V=18.2 about 10 hours after the burst the optical
afterglow was the brightest so far detected by Swift and one of the brightest
optical afterglows ever seen. The Burst Alert Telescope (BAT) light curves show
three fast-rise-exponential-decay spikes with $T_{90}$=12s and a fluence of
7.6$\times 10^{-6}$ ergs cm$^{-2}$ in the 15-150 keV band. With an $E_{\rm
\gamma, iso} = 1.26 \times 10^{54}$ ergs it was also one of the most energetic
bursts of all times. The Swift spacecraft began observing of the afterglow with
the narrow-field instruments about 10 hours after the detection of the burst.
The burst was bright enough to be detected by the Swift UV/Optical telescope
(UVOT) for almost 3 days and by the X-ray Telescope (XRT) for a week after the
burst. The X-ray light curve shows a rapidly fading afterglow with a decay
index $\alpha$=1.76$^{+0.15}_{-0.07}$. The X-ray energy spectral index was
$\beta_{\rm X}$=0.71\plm0.10 with the column density in agreement with the
Galactic value. The spectral analysis does not show an obvious change in the
X-ray spectral slope over time. The optical UVOT light curve decays with a
slope of $\alpha$=1.8\plm0.2.
  The steepness and the similarity of the optical and X-ray decay rates suggest
that the afterglow was observed after the jet break. We estimate a jet opening
angle of about 1-2$^{\circ}$
