This PhD explores the growth and spread of the global jihad movement in the West and its success in radicalising Western Muslims. In order to explain this phenomenon it analyses the work of one of the movement’s most influential English-speaking ideologues, Anwar al-Awlaki. This will reveal how he “Westernised” global jihadist ideology so that it could be made more accessible to his audience. The primary aim of this study is to demonstrate how Awlaki’s success in making the key tenets of global jihadist ideology accessible to Westerners impacted upon the radicalisation process of homegrown jihadists. In the first instance, this study will place Awlaki in the context of a decades-long effort by global jihadist strategists to create a social movement capable of appealing to audiences around the globe. In order for this strategy to succeed in the West, the movement required an effective interpreter and the thesis will show how Awlaki was able to fulfil this role by pursuing a number of processes related to social movement leadership. The subsequent analysis of Awlaki’s work will shed light on both his own radicalisation from non-violent Islamist to global jihadist and his later efforts to spread this violent ideology in the West. Following this, a number of individual cases of Western Muslim radicalisation will be analysed, showing how Awlaki influenced their decision-making process. This approach will allow the author to highlight the importance of an increased emphasis on the connection between extremist ideas and violent action, which it will be argued lies at the heart of homegrown jihadist radicalisation in the West.