We provide a catalog of ~100,000 candidate young stellar objects (YSOs) derived from the GLIMPSE survey and its extensions, including GLIMPSE I, II, 3D, Vela-Carina, Cygnus X, and SMOG, providing coverage of 613 square degrees of the inner Galaxy toward the mid-plane. Our YSO selection strategy is designed to make maximum use of the IRAC photometry’s high spatial resolution and sensitivity, augmented by near-infrared catalogs, to identify sources with infrared excess, while maintaining contamination rates that are similar to the cleanest published Spitzer YSO catalogs of massive star-forming regions. We use a random forest classifier trained with YSOs identified in the Massive Young Star-Forming Complex Study in Infrared and X-ray (MYStIX). We present infrared color-color diagrams to explain how classifications are made, and we identify subsets of objects with strong silicate absorption or polycyclic aeromatic hydrocarbon emission. Using Gaia astrometry, we examine the three-dimensional spatial clustering of YSOs in the Galaxy and find that many groups of YSOs are associated with the Sagittarius-Carina and Scutum-Centaurus arms of the Galaxy. Using Zwicky Transient Facility light curves, we find that the YSO candidates typically have higher variability amplitudes than field stars, and that many of the light curves exhibit dipping and bursting behaviors characteristic of YSOs.