In this article, we present data from the first dedicated census of commemorative antimafia street names in Italian cities, investigating streets named after innocent victims of the mafia as “lieux de memoire”. We introduce the concept of social amnesia surrounding the mafia to cast light on the impact of mafia violence on socio-spatial relationships and potential societal responses to this trauma. The practice of naming streets to commemorate the antimafia movement is a strategy for countering social amnesia. Antimafia street names are forms of urban resistance and civic education, and as such may be defined as a “common good”. Nonetheless, antimafia street naming can also be a primarily formal or acritical memory practice or – potentially – an expedient for legitimizing illegal relations. This kind of ambiguity is inherent in mafia studies and attests to the ongoing urban conflict between the mafia and the antimafia movement.