A key challenge preventing the widespread deployment of direct ammonia fuel cells (DAFCs) is the lack of inexpensive, active, and poison-resistant anode catalysts capable of efficiently carrying out the ammonia oxidation reaction (AOR). While transition-metal catalysts such as Pt exhibit good activity, their susceptibility to *N poisoning and high cost significantly limit their feasibility. Ceria (CeO2) has shown potential in related electrocatalytic reactions due to facet-dependent reducibility, oxygen vacancy formation, and tunable surface electronic structure. However, a comprehensive mechanistic understanding of AOR on ceria surfaces is lacking. Thus, this work outlines a density functional theory (DFT) investigation of AOR across the low-index ceria facets (111), (110), and (100) to identify the most active and selective surface for ammonia electrooxidation. Preliminary calculations reveal that the AOR intermediates were ~0.3 eV more stable when accounting for spin-polarization relative to non-spin-polarized, demonstrating the significant role magnetic moments play for AOR on low-index ceria surfaces. Additionally, ceria (100) is predicted to be the most active surface due to having the greatest surface energy compared to ceria (110) and ceria (111); however, further calculations are required to confirm this trend for AOR.