Spitzer IRAC observations and stellar photometric catalogs are presented for the Massive Young star-forming complex Study in the Infrared and X-ray (MYStIX). MYStIX is a multiwavelength census of young stellar members of 20 nearby (d<4kpc), Galactic, star-forming regions that contain at least one O star. All regions have data available from the Spitzer Space Telescope consisting of GLIMPSE or other published catalogs for 11 regions and results of our own photometric analysis of archival data for the remaining 9 regions. This paper seeks to construct deep and reliable catalogs of sources from the Spitzer images. Mid-infrared study of these regions faces challenges of crowding and high nebulosity. Our new catalogs typically contain fainter sources than existing Spitzer studies, which improves the match rate to Chandra X-ray sources that are likely to be young stars, but increases the possibility of spurious point-source detections, especially peaks in the nebulosity. IRAC color-color diagrams help distinguish spurious detections of nebular polycyclic aromatic hydrocarbon emission from the infrared excess associated with dusty disks around young stars. The distributions of sources on the mid-infrared color-magnitude and color-color diagrams reflect differences between MYStIX regions, including astrophysical effects such as stellar ages and disk evolution.