1. Megaherbivores have been lost from most ecosystems worldwide and current increases in poaching of rhino and elephant spp. threaten their status in the systems where they still occur. Although megaherbivores are said to be key drivers of ecosystem structure and functioning, empirical evidence is strongly biased to studies on African elephants. We urgently need a better understanding of the impact of other megaherbivore species to predict the consequences of megaherbivore loss.2.We used a unique ‘recolonization experiment’ to test how a megagrazer, white rhinoceros, is affecting the structure of savanna grasslands in Kruger National Park (KNP).3. With a 30-year record of rhinoceros distribution, we quantified how they recolonized KNP following their re-introduction. This allowed us to identify landscapes with high rhino densities and a long time since recolonization versus landscapes with low rhino densities that were recolonized more recently but were otherwise biophysically similar. We recorded grassland heterogeneity on 40 transects covering a total of 30 km distributed across both landscapes. We used two proxies of grassland heterogeneity;% short grass cover and number of grazing lawn patches. Grazing lawns are patches with specific communities of prostrate-growing stoloniferous short grass species.4.Short grass cover was clearly higher in the high rhino impact (17.5%) than the low rhino impact landscape (10.7%). Moreover, we encountered 20 times more grazing lawns in the high rhino impact landscape. The effect of rhino on a number of lawns and on the short-grass cover was similar for the two dominant geologies in KNP, basalt-derived versus granite-derived soils.5.Synthesis. We provide empirical evidence that white rhinoceros may have started to change the structure and composition of Kruger National Park&apos’s savanna grasslands. It remains to be tested if these changes lead to other ecological cascading effects. However, our results highlight that the current rhino poaching crisis may not only affect the species but threaten the potentially key role of this megaherbivore as a driver of savanna functioning. This article is protected by copyright. All rights reserved.