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We present the first high spatial resolution Chandra X-ray study of NGC 2244,the 2 Myr old stellar cluster immersed in the Rosette Nebula. Over 900 X-raysources are detected; 77% have optical or FLAMINGOS near-infrared (NIR) stellarcounterparts and are mostly previously uncatalogued young stellar clustermembers. All known OB stars with spectral type earlier than B1 are detected andthe X-ray selected stellar population is estimated to be nearly completebetween 0.5 and 3 Msun. The X-ray luminosity function (XLF) ranges from29.4<logLx<32 ergs/s in the hard (2-8keV) band. By comparing the NGC 2244 andOrion Nebula Cluster XLFs, we estimate a total population of 2000 stars in NGC2244. A number of further results emerge from our analysis: The XLF and theassociated K-band luminosity function indicate a normal Salpeter initial massfunction (IMF) for NGC 2244. This is inconsistent with the top-heavy IMFreported from earlier optical studies that lacked a good census of <4Msunstars. The spatial distribution of X-ray stars is strongly concentrated aroundthe central O5 star, HD 46150. The other early O star, HD 46223, has fewcompanions. The cluster's stellar radial density profile shows two distinctivestructures. This double structure, combined with the absence of masssegregation, indicates that this cluster is not in dynamical equilibrium. Thespatial distribution of X-ray selected K-excess disk stars and embedded starsis asymmetric with an apparent deficit towards the north. The fraction ofX-ray-selected cluster members with K-band excesses caused by innerprotoplanetary disks is 6%, slightly lower than the 10% disk fraction estimatedfrom the FLAMINGOS study based on the NIR-selected sample. This is due to thehigh efficiency of X-ray surveys in locating disk-free T Tauri stars.[Abridged]

A Chandra Study of the Rosette Star-Forming Complex. I. The Stellar Population and Structure of the Young Open Cluster NGC 2244