While corroborating the fact that the majority of protesters attend demonstrations together with friends, family and/or fellow members of their organizations, this article shows that protesting alone remains an option for many people – under the right circumstances. Through multilevel analysis of survey data from participants in 69 demonstrations in eight Western European countries, the authors study lone protesters in different types of demonstrations. On the individual level, they show that protesting alone is closely linked to relative detachment from interpersonal mobilizing networks, as well as to short decision times. The authors also develop demonstration-level explanations for why lone protesters are more common in some demonstrations than in others. Precipitating events and inclusive social movement communities increase the proportion of lone demonstrators, which is also higher in static rallies than in moving demonstrations. These factors arguably make personal networks less crucial for protest mobilization.