  We report X-ray observations of the field containing the ultraluminous IRAS
galaxy Mrk~273 Using the ACIS-S3 instrument on board Chandra. The high
resolution X-ray image, for the first time, reveals a compact hard X-ray
nucleus in Mrk~273. Its X-ray energy distribution is well described by a
heavily obscured power-law spectrum plus a narrow $\Feka$ emission line at 6.4
keV. The neutral hydrogen column density is about $4\times10^{23}\cm^{-2}$,
implying an absorption -corrected X-ray luminosity (0.1--10 keV) for the
nucleus of $\Lx\approx 6.5\times 10^{43} \ergs$. There are also bright soft
X-ray clumps and diffuse soft X-ray emissions surrounding the central hard
X-ray nucleus within the $10\arcsec$ of the nuclear region. Its spectrum can be
fitted by a MEKAL thermal model with temperature of about 0.8 keV and high
metallicity ($Z\sim 1.5Z_\odot$) plus emission lines from $\alpha$ elements and
ions. Further outside the central region, the Chandra observations reveal a
very extended hot gas halo with a projected diameter of about $108 \kpc\times
68 \kpc$ and soft X-ray luminosity of $\Lx\approx 1.9\times 10^{41} \ergs$. The
temperature of the hot gas is about 0.62 keV with a low metallicity ($Z \sim
0.1 Z_\odot$). We discuss the nature of the AGN in Mrk~273 and the implications
of our results on the origin of X-ray halos in elliptical galaxies. We also
discuss the properties of Mrk~273x, a background AGN in the Mrk~273 field. The
AGN has an X-ray luminosity of $\Lx \approx 2.43\times 10^{44}\ergs$ in the
0.5-10 keV band. Its X-ray properties resemble those of Seyfert 1 galaxies
while its optical properties are similar to Seyfert 2 galaxies. Such mixed
classifications may be a challenge for the unification scheme of AGNs.
