  We obtained a 108 ks Chandra X-ray Observatory (CXO) observation of PSR
J1849-0001 and its pulsar wind nebula (PWN), coincident with the TeV source
HESS J1849-000. By analyzing the new and archival CXO data, we resolved the
pulsar from the PWN, explored the PWN morphology on arcsecond and arcminute
scales, and measured the spectra of different regions of the PWN. Both the
pulsar and the compact inner PWN spectra are hard with power-law photon indices
of $1.20 \pm 0.07$ and $1.49 \pm 0.20$, respectively. The jet-dominiated PWN
has a relatively low luminosity, lack of gamma-ray pulsations, relatively hard
and nonthermal spectrum of the pulsar, and sine-like pulse profile, which
indicates a relatively small angle between the pulsar's spin and magnetic
dipole axis. In this respect, it shares similar properties with a few other
so-called MeV pulsars. Although the joint X-ray and TeV spectral energy
distribution can be roughly described by a single-zone model, the obtained
magnetic field value is unrealistically low. A more realistic scenario is the
presence of a relic PWN, no longer emitting synchrotron X-rays but still
radiating in TeV via inverse-Compton upscattering. We calso serendipitously
detected surprisingly bright X-ray emission from a very wide binary whose
components should not be interacting.
