  The young massive OB association Cygnus OB2, in the Cygnus X complex, is the
closest (1400 pc) star forming region to the Sun hosting thousands of young low
mass stars and up to 1000 OB stars, among which are some of the most massive
stars known in our Galaxy. This region holds great importance for several
fields of modern astrophysics, such as the study of the physical properties of
massive and young low-mass stars and the feedback provided by massive stars on
star and planet formation process. Cygnus OB2 has been recently observed with
Chandra/ACIS-I as part of the 1.08Msec Chandra Cygnus OB2 Legacy Project. This
survey detected 7924 X-ray sources in a square degree area centered on Cyg OB2.
Since a proper classification and study of the observed X-ray sources also
requires the analysis of their optical and infrared counterparts, we combined a
large and deep set of optical and infrared catalogs available for this region
with our new X-ray catalog. In this paper we describe the matching procedure
and present the combined catalog containing 5703 sources. We also briefly
discuss the nature of the X-ray sources with optical and infrared counterparts
using their position in the color-magnitude and color-color diagrams.
