Religious persecution is a worldwide phenomenon. Acts of intolerance, discrimination, and persecution based on religion or belief have become part of our daily life. Believers of every faith, including Christians, Muslims, Buddhists, Jews and Hindus in many parts of the world, face serious discrimination, restrictions and sometimes severe persecution for practising their faith. This study focuses on internal persecution among Muslims. Internal persecution within the Islamic tradition means the persecution of Muslims by other Muslims, what might be characterised as "intra-religious" as opposed tot "inter-religious" persecution. This type exposes the political and sociological nature of religious persecution, since the persecuted group is of the same religion as the persecuting majority. This study also helps to challenge the alleged religious rationale of such persecution in that every religious majority was in the past, and may become in future, a minority. Thus, protection of freedom of religion and belief is essential for the validity and authenticity of all religious beliefs and practices, whether of a majority or a minority. For the purpose of understanding the phenomenon, three case studies (the Ahmadiyya in Pakistan, the Shi'is in Saudi Arabia and the Republican Brothers in Sudan) are analysed. From the conclusions of these cases, a contextual framework for understanding and combating intra-religious persecution is outlined.