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Abstract: Extreme geomagnetic storms pose significant risks to spacecraft operations through enhanced particle radiation, geomagnetic disturbances, and thermospheric density variations. In this study, we comparatively analyze three extreme geomagnetic storms with minimum Dst indices below − 350 nT: October 29–31, 2003, November 20–22, 2003, and May 10–12, 2024. Using space- and ground-based observations, we examine the associated solar flares, coronal mass ejections (CMEs), interplanetary conditions, high-energy particle environments at geosynchronous orbit, and reported spacecraft impacts. Although the three storms exhibited comparable geomagnetic intensities, their solar and interplanetary drivers differed substantially, including fast CMEs, a slower but magnetically intense ICME, and a complex merged-CME structure. In addition, the magnitudes of the solar proton events (SPEs) varied considerably. The magnitude of proton event magnitude is primarily related to CME speed, whereas geomagnetic storm intensity depends on the combined effects of CME speed, the southward magnetic field component, and its duration. Furthermore, CME speed is found to correlate well with the fluence of the associated soft X-ray flare. The relatively limited spacecraft impacts during the November 2003 and May 2024 storms are likely attributable to weaker proton enhancements compared with October 2003. These results highlight the importance of considering CME speed and X-ray flare fluence, in addition to geomagnetic indices, for spacecraft risk assessment and extreme space weather forecasting.