Korean television showed a somber Kim standing beneath two towering statues of his grandfather and his late father, Kim Jong Il, while receiving applause from party functionaries and the military. Kim Jong Il was given the title of "eternal general secretary" of the Workers' Party, while Kim Jong Un was named the party's first secretary.
The title appears to be a newly created position that sets the stage for a virtual coronation of Kim Jong Un, says North Korea watcher Jonathan Pollack of the Washington-based Brookings Institution.
"Creating this new position is sort of like retiring a jersey number for a famous baseball player," Pollack said. "It shows a deference to his father and to the old guard, while still cementing his control on power."
North Korea announced other titles for Kim Jong Un, including making him a member of the Political Bureau of the Central Committee and chairman of the Central Military Commission.
Kim Jong Un was already being described as the supreme leader of the party, state and army. But it is unclear how directly the young Kim, thought to be in his late 20s, is involved in policy decisions.
The leadership transition bears similarities to the previous transfer of power from one generation of the Kim family to another.
"Kim Jong Il is now venerated at the same level as his father, buried in the same tomb, and they are making statues of them riding together on horseback," Pollack said.
"But Kim Jong Un never got the on-the-job training his father did, so he may have this title to allow some mentoring or sharing power and decisions with his elders."