Title: Ultra-High Energy Cosmic Ray Energy Spectrum using Hybrid Analysis with TAx4 Abstract: Cosmic rays are subatomic particles of extraterrestrial origin and at the highest energies, they are not well understood. The variation of the cosmic ray flux with energy is referred to as the “Energy Spectrum.” The measurement of the cosmic ray energy spectrum is important because it may give a hint of where cosmic rays come from. The Telescope Array (TA) Cosmic Ray Observatory, located in Millard County Utah, is the largest cosmic ray detector in the Northern hemisphere. Following evidence for a hotspot in the arrival directions of the highest energy cosmic rays, TA underwent the TAx4 upgrade to expand the area of Surface Detectors (SD) by a factor of 4. The upgrade included new Fluorescence Detector (FD) stations to view over the expanded SD arrays. In this work, I will present a preliminary cosmic ray energy spectrum using hybrid events fromTAx4, the hybrid resolutions of the detector, and data-MC comparisons. I will show this work’s preliminary hybrid energy spectrum is in agreement with previous TA measurements, which is a key first step towards future composition and anisotropy studies.