'Citizenship' is considered to be a 'fundamental right' of an individual within the boundary of state of his/her origin. The democratic countries of the world thus have ensured 'right to citizenship' in their constitutions. But 'citizenship' has remained a 'contested one' for a considerable number of 'forced' and 'voluntary' migrants of the south Asian countries as well as for the dwellers of the Ondo Bangladeshi enclaves (popularly called chhitmahals). After critically analyzing the historical development in India, Bangladesh, Myanmar and Bhutan, this book has examined the constitutional provisions of citizenship, citizenship acts, nature of statelssness' and nation building process in India, Bhutan and Bangladesh with a perspective of migration studies.