This study provides a detailed analysis of the impact of the magnetic storm (referred to as the Victory Day Storm, as the solar flares occurred on May 8–9, 2024), which took place from May 10 to 12, 2024, and has become the most significant geomagnetic event of the 21st century to date, on the subauroral and mid-latitude ionosphere using a variety of instruments and observation methods. The research is based on data from satellite systems (Swarm, DMSP, TIMED), ground-based magnetometers, ionosondes, VLF (very low frequency) signals, GNSS (global navigation satellite system) receivers, and all-sky cameras. The solar flares and powerful coronal mass ejection (CME) from the Sun caused intense geomagnetic disturbances, leading to significant changes in the density, structure, and dynamics of the ionospheric plasma at subauroral and mid-latitudes. In particular, auroras were observed at these latitudes, which is a rare phenomenon for these regions. Satellite observations, SUSSI data (allowing for measurements of auroral emissions in the ionosphere) from the DMSP satellite, and all-sky cameras provided detailed information on the spatial development of storm phenomena in the ionosphere. The cooling flux of nitrogen oxide during geomagnetic activity was studied using TIMED/SABER data, as well as latitudinal profiles of the integral O/N2 ratio from TIMED/GUVI data. Measurements from magnetometers and ionosondes revealed significant changes in the magnetic field and ionospheric plasma density, while VLF (very low frequency) stations and GNSS receivers recorded substantial disruptions in radio communication and navigation during the Victory Day Geomagnetic Storm. The study emphasizes the need for integrating various data to deeply understand and predict the impact of extreme magnetic storms on the ionosphere, upper atmosphere, and related technological systems. © 2025 COSPAR. Published by Elsevier B.V. All rights are reserved, including those for text and data mining, AI training, and similar technologies.