Daniel or Rajan Roy) (11 August 1923 – 27 March 2005) was an Indian Nagercoil born physicist who worked in the fields of cosmic rays and space physics, and remained Director Chairman of Tata Institute of Fundamental Research.
He also served as an advisor to the prime minister of India, Indira Gandhi in 1976.
He worked in the field of cosmic rays with Homi Jehangir Bhabha for 23 years.
He was awarded the Padma Bhushan in 1992 by the Government of India, for his contributions to science and engineering.