This thesis examines how mobile phones affect political activity. In a number of cases, the mobile phone as a uniquely easy-to-use and personal communication device has been a key tool to facilitate mobilization and collective action, such as during the impeachment process of President Estrada of the Philippines in 2001. Taking some of these case studies as a starting point, I find a plausible theoretical framework for analysis in the literature on collective action theory, mobilization and diffusion theory, and network society theory, which I develop further to include the novel aspect of mobile telecommunications. Mobile teledensity data and three political activism indicators in 191 countries are then tested with negative binomial Poisson and ordinal logistic regression over a period of 16 years. The results do not confirm the observations of the earlier case studies; I find no significant relationship between mobile teledensity and anti-government protests, riots, or major government crises.