This chapter addresses the relatively recent phenomenon of Islamist militants and home-grown terrorism perpetrated by Muslims in the West. Although Muslims have resided in Western countries for centuries, with large communities having been established since the 1960s and 1970s, home-grown Islamist terrorism is a very new phenomenon that emerged in the first decade of the twenty-first century. Following the provision of some key definitions of terrorism, home-grown terrorism, radicalisation, Islamism, and jihadism, this chapter identifies some of the major Islamist terrorist attacks in the West and several perspectives that attempt to explain the phenomenon. It discusses several models of radicalisation and research pertaining to its relationship with Muslim integration. This chapter examines some reoccurring characteristics of home-grown jihadists, including age, gender, and education. The social component of home-grown terrorism is also discussed, including how prisons and the Internet facilitate the radicalisation process. The chapter examines the roles of ideology and religion and discusses the most commonly used methods in countering radicalisation.