  We present the most extensive and detailed reddening maps of the Magellanic
Clouds (MCs) derived from the color properties of Red Clump (RC) stars. The
analysis is based on the deep photometric maps from the fourth phase of the
Optical Gravitational Lensing Experiment (OGLE-IV), covering approximately 670
deg2 of the sky in the Magellanic System region. The resulting maps provide
reddening information for 180 deg2 in the Large Magellanic Cloud (LMC) and 75
deg2 in the Small Magellanic Cloud (SMC), with a resolution of 1.7x1.7 arcmin
in the central parts of the MCs, decreasing to approximately 27x27 arcmin in
the outskirts. The mean reddening is E(V-I) = 0.100 +- 0.043 mag in the LMC and
E(V-I) = 0.047 +- 0.025 mag in the SMC. We refine methods of calculating the RC
color to obtain the highest possible accuracy of reddening maps based on RC
stars. Using spectroscopy of red giants, we find the metallicity gradient in
both MCs, which causes a slight decrease of the intrinsic RC color with
distance from the galaxy center of ~0.002 mag/deg in the LMC and between 0.003
and 0.009 mag/deg in the SMC. The central values of the intrinsic RC color are
0.886 and 0.877 mag in the LMC and SMC, respectively. The reddening map of the
MCs is available on-line both in the downloadable form and as an interactive
interface.
