Step 1: Understanding the Question:
The question asks to identify a former Prime Minister of India who had also served as the Governor of the Reserve Bank of India (RBI).
Step 2: Detailed Explanation:
Dr. Manmohan Singh, an acclaimed economist, held several key positions in the Government of India before becoming Prime Minister.
- He served as the Governor of the Reserve Bank of India from 16 September 1982 to 14 January 1985.
- He later served as the Finance Minister of India from 1991 to 1996, where he is credited with ushering in an era of economic reforms.
- He then served two terms as the Prime Minister of India from 2004 to 2014.
The other Prime Ministers listed did not hold the position of RBI Governor.
Step 3: Final Answer
Dr. Manmohan Singh is the Prime Minister who also served as the Governor of the Reserve Bank of India.