  The Orion Nebula is one of the most frequently observed nearby (<1
kiloparsec) star forming regions and, consequently, the subject of a large
bibliography of observations and interpretation. The summary in this chapter is
bounded spatially by the blister HII region, with sources beyond the central
nebula that are part of the same dynamical clustering covered in other chapters
in this book. Herein are discussed panchromatic observations of the massive OB
stars, the general T Tauri population, the sub-stellar sources and variable
stars within the Orion Nebula. First, a brief history of 400 years of
observation of the Nebula is presented. As this history is marked clearly by
revelations provided in each age of new technology, recent ultra-deep X-ray
surveys and high resolution multi-epoch monitoring of massive binary systems
and radio stars receive special attention in this review. Topics discussed
include the kinematics, multiplicity, mass distribution, rotation, and
circumstellar characteristics of the pre-main sequence population. Also treated
in depth are historical and current constraints on the distance to the Orion
Nebula Cluster; a long standing 10-20% uncertainty has only recently begun to
converge on a value near ~400 parsecs. Complementing the current review of the
stellar population is a companion chapter reviewing the molecular cloud,
ionized HII region and the youngest protostellar sources.

Astrophysics