This thesis examines Sikh groups in Britain and the implications these have for criteria related to the issue of Sikh identity. Five groups have been selected. They are: the Guru Nanak Nishkam Sewak Jama; the Namdharis; the Ravidasls; the Valmikis; and the Sikh Dharma of the Western Hemisphere, which is also frequently associated with the Healthy, Happy, Holy Organization (3HO). The thesis begins with a historical analysis of Sikhism, to discover what it meant to be a Sikh in the days of the founder of the faith, Guru Nanak, and during the time of the successive Gurus. Political and social issues related to the development of Sikhism and emerging Sikh identity are examined also at the outset. Each group has its own unique contribution to make towards highlighting certain indicators and inhibitors of a Sikh identity. Thus, an important part of the present thesis is to examine the beliefs and practices of each group in order to assess its contribution towards a Sikh identity. Each group has unique leaders and founders; it is interesting, therefore, to see what implications the leaders' backgrounds and teachings have on the ethos of the group studied. The present thesis has aimed to highlight the implications of five groups ~ who have in the present and/or in the past have Sikh connections ~ on issues related to Sikh identity. This has been undertaken by continuous reference to four fundamental questions. A thematic approach was adopted for concluding the thesis. Each of the themes arose as significant factors developed throughout the research. The themes illustrate areas that are responsible for the promotion, as well as the hindering, of a uniform Sikh identity among the groups. The five themes that emerged were: (1) The concept of Guru in Sikhism; (2) Leaders and founders; (3) The role of the Rehat Maryada in relation to Sikh identity; (4) Caste and the Panth; (5) The issue of Sikh identity in relation to Punjabi ethnicity. The present research has shown that there are no overall dominant criteria with which to assess the Sikh identity of the Sikh community as a whole. Thus, contrary, to prevalent views about the Sikhs, there are many different "types" of Sikhs present today. I have suggested a federal identity of the Sikh community as a whole. This implies a unity of Sikhs worldwide but independence in the interpretation of Sikhism for the different groups. A federal identity might mean one or two core beliefs such as the acceptance of the Sikh Gurus' teachings and belief in the Sikh Absolute -- but, further than that, it is up to the individual group to express its unique beliefs and practices.