We analyze Synthetic Aperture Radar Interferometry (InSAR) and Global Navigation Satellite System (GNSS) data to characterize ground deformation and dike opening associated with the May 2021 Nyiragongo eruption. Despite well-documented eruptions in 1977 and 2002, Nyiragongo’s magmatic system and its interaction with regional rifting remain poorly understood. Here, we use Sentinel-1 (ESA Copernicus) and ALOS-2 (JAXA) InSAR data and GNSS observations, from the KivuGNet network, covering the period of the eruption and dike intrusion. Deformation is dominated by a southward-propagating co-eruptive dike intrusion extending over 25 km, accompanied by surface ruptures and ground fissures of about 1.5 meters in Goma (Democratic Republic of Congo) and Gisenyi (Rwanda). Joint inversions of four interferograms with GNSS data resolved a maximum dike opening near 10 meters and a volumetric increase of about 180 Mm 3 . The inferred dike geometry aligns with observed ground deformation and seismicity, underscoring the coupling between magmatic and tectonic processes.