This review explores the potential for utilizing Sustainable Aviation Fuels (SAFs) in internal combustion piston engines across aviation, automotive, marine, and military applications. While SAFs have been primarily developed for turbine engines, certain paraffinic variants—such as HEFA and FT-SPK—demonstrate high compatibility with compression-ignition (CI) engines due to their favorable combustion characteristics, including high cetane number, low sulfur content, and clean-burning profiles. The feasibility of using SAFs in spark-ignition (SI) engines remains limited, primarily due to low octane numbers of current SAF formulations, although ongoing research into high-octane synthetic fuels is promising. The article examines SAF production pathways, fuel standards, material compatibility, emissions impact, and regulatory frameworks. Results from laboratory and field studies indicate that SAFs can reduce particulate matter, CO, unburned hydrocarbons, and overall engine wear while offering 60–85% life-cycle greenhouse gas (GHG) reduction depending on feedstock and process. However, challenges such as fuel availability, cost, seal swell compatibility, and certification barriers persist. Given these findings, SAFs—particularly in drop-in CI applications—offer a practical and immediate strategy for decarbonizing legacy fleets without major infrastructure changes. For SI engines, further fuel development and certification are needed. The integration of SAFs into piston engines represents a valuable bridge solution toward sustainable propulsion in sectors difficult to electrify, provided that scaling, economic, and environmental sustainability concerns are effectively addressed.