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We present the first high spatial resolution X-ray study of the massive starforming region NGC 6357, obtained in a 38 ks Chandra/ACIS observation. Insidethe brightest constituent of this large HII region complex is the massive opencluster Pismis 24. It contains two of the brightest and bluest stars known, yetremains poorly studied; only a handful of optically bright stellar members havebeen identified. We investigate the cluster extent and Initial Mass Functionand detect ~800 X-ray sources with a limiting sensitivity of 10^{30} ergss^{-1}; this provides the first reliable probe of the rich intermediate-massand low-mass population of this massive cluster, increasing the number of knownmembers from optical study by a factor of ~50. The high luminosity end (logL_h[2-8 keV]\ge 30.3 ergs s^{-1}) of the observed X-ray luminosity function inNGC 6357 is clearly consistent with a power law relation as seen in the OrionNebula Cluster and Cepheus B, yielding the first estimate of NGC 6357's totalcluster population, a few times the known Orion population. We investigate thestructure of the cluster, finding small-scale substructures superposed on aspherical cluster with 6 pc extent, and discuss its relationship to the nebularmorphology. The long-standing Lx - 10^{-7}L_{bol} correlation for O stars isconfirmed. Twenty-four candidate O stars and one possible new obscured massiveYSO or Wolf-Rayet star are presented. Many cluster members are estimated to beintermediate-mass stars from available infrared photometry (assuming an age of1 Myr), but only a few exhibit K-band excess. We report the first detection ofX-ray emission from an Evaporating Gaseous Globule at the tip of a molecularpillar; this source is likely a B0-B2 protostar.Comment: 64 pages (double columns), 9 table, 17 figures (reduced resolution),  ApJ accepted. Please contact J. Wang for full table

An X‐Ray Census of Young Stars in the Massive Southern Star‐forming Complex NGC 6357