  In this first of two companion papers on the Orion Nebula Cluster (ONC), we
present our analysis of a 63 Ksec Chandra HRC-I observation that yielded 742
X-ray detections within the 30'x30' field of view. To facilitate our
interpretation of the X-ray image, here we collect a multi-wavelength catalog
of nearly 2900 known objects in the region by combining 17 different catalogs
from the recent literature. We define two reference groups: an infrared sample,
containing all objects detected in the K band, and an optical sample comprising
low extinction, well characterized ONC members. We show for both samples that
field object contamination is generally low.
  Our X-ray sources are primarily low mass ONC members. The detection rate for
optical sample stars increases monotonically with stellar mass from zero at the
brown dwarf limit to ~100% for the most massive stars but shows a pronounced
dip between 2 and 10 solar masses.
  We determine L_X and L_X/L_{bol} for all stars in our optical sample and
utilize this information in our companion paper to study correlations between
X-ray activity and other stellar parameters.
