Islamophobia is not a new term but it has become commonly used in the United States following the 9/11 terrorist attacks. This entry provides an overview of the demographics of the Muslim population in the United States. The historical context in which the use of the term first emerged is then identified, followed by a discussion of the two major approaches to defining Islamophobia. The term connotes either outright anti-Muslim bigotry due to religious intolerance or racism and xenophobia toward people from the Middle East, North Africa, and South Asia who are Muslim or who have a “Muslim-like” appearance. The history of anti-Muslim bigotry in the United States is traced from before the founding of the nation through present times. Implications are presented for social work with Muslim clients, organizations, and communities who may be impacted by anti-Muslim bigotry.