56-year-old Rohinton Nariman was appointed as the Solicitor General (SG), the second senior-most law officer of the country, on July 23, 2011.
Sources said that Mr Nariman has not given any reason for quitting his post in his resignation letter.
There has been speculation Nariman was unhappy over certain directions of Law Minister Ashwani Kumar and the ministry.
He was appointed after the then Solicitor General Gopal Subramaniam had resigned on July 14, 2011. Mr Subramaniam had resigned after Mr Nariman was appointed as special counsel to defend Telecom Minister Kapil Sibal in Supreme Court in the 2G case, apparently without his knowledge.
Mr Nariman is the son of eminent jurist Fali S Nariman.
He argued for Mukesh Ambani's RIL along with senior advocate Harish Salve in the dispute over the supply and pricing of gas from KG basin between the Ambani brothers.
Mr Nariman was designated as a senior advocate at the age of 37 years in 1993 when the then Chief Justice of India M N Venkatachaliah amended the rules, for designating a lawyer as a senior advocate, by reducing the minimum age limit of 45 years.
He joined the Bar as an advocate in 1974 after completing his LL.B from Campus Law Centre, Delhi University, where he was among the toppers.
He had also gone to Harvard University for further studies.