The oath of office was administered by chief justice of Jammu and Kashmir high court Geeta Mittal at a simple function held at Leh.
Radha Krishna Mathur was formerly the Chief Information Commissioner.
Mathur is a retired 1977-batch IAS officer of Tripura cadre. He retired as the Chief Information Commissioner of India (CIC) in November 2018.
Indian Administrative Service (IAS) 0fficer Umang Narula has been appointed Advisor to the Lieutenant Governor of the Union Territory of Ladakh with effect from October 31.
"In exercise of the powers conferred by sub-section(4) of Section 58 of the Jammu and Kashmir Reorganisation Act, 2019, the government of India appoints Umang Narula, IAS as advisor to the Lieutenant Governor of the Union Territory of Ladakh with effect from October 31, 2019, until further orders," the Ministry of Home Affairs said in its order.
The two new Union Territories of Jammu and Kashmir and Ladakh came into being on Thursday midnight, putting into effect the reorganization of the erstwhile state.
Watch: Exclsuive interview of Radha Krishna Mathur
The implementation of the Jammu and Kashmir Reorganisation Act, 2019, which got President's assent on August 9, means the special status enjoyed by Jammu and Kashmir under Article 370 comes to an end after 72 years.
The landmark bill to abolish special status of Jammu and Kashmir and bifurcate the state into two Union Territories was moved in Parliament on August 5 and passed the next day by both Houses, amidst much uproar.
According to the Act, the UT of J&K will have a legislature while the UT of Ladakh will have no legislature.
Watch the swearing-in ceremony of Ladakh Lt Governor