P. S. Krishnan is a former member of the Indian Administrative Service (IAS) and has been actively working for the cause of the advancement and empowerment of the deprived social categories of Indian society, the Scheduled Castes, Scheduled Tribes and Backward Classes, for over nearly seven decades including his 35-year career in the IAS. He has been Secretary, Ministry of Welfare, Government of India; Member, National Commission for Scheduled Castes and Scheduled Tribes; Member-Secretary, National Commission for Backward Classes; and Chairman/Member of different Steering Committees and Working Groups of India's Planning Commission. He has been Honorary Advisor to the central government and certain State governments in matters relating to the disadvantaged social categories and guides many social organizations and activists. He has published books, papers and articles extensively.