In SE France, where most wildfires occur, the fire size has never exceeded 6744 ha whereas mega-fires have already burned huge areas in other Mediterranean countries such as Spain or Portugal. It was interesting to find out what main factors drove the ignition of the largest fires having occurred in this region. The study was carried out on the forest fires database Prométhée, recording all the forest fires in the 15 département of SE France since 1973. However, the records before 1997 being not reliable, only the period 1997-2010 was investigated. Only 1% of the fires (N=260) recorded during this period were larger than 100ha whereas 78% of the fires were smaller than 1ha. However these large fires accounted for 71% of the burned area and 66% of these fires occurred during the summer (July-August). The number of large fires and the burned area per year and per département were calculated and the proportions of fires causes were determined. In each département, the impact of different explanatory variables, such the population density, the proportion of land covers, the number of dry months and the dry severity index (de Matonne index, IM), on the number of large fires and on the burned area was investigated using a multivariate analysis (Co-inertia analysis). Results showed that high values in shrubland and pasture covers, population density and number of dry months had a positive impact on the number of large fires whereas high values in forest cover, spring and fall-winter IM had a negative impact on this parameter. High values in natural vegetation cover, especially the shrubland cover, fall-winter IM and number of dry months had a positive impact on the burned area whereas high values in summer IM, farmland and pasture covers and population density had a negative impact on this parameter. The départements the most affected by such fires are those situated at the eastern part of the region on the outskirts of the Mediterranean Sea and, in each one of them, the main fire cause is arson.