Stockholm's chief prosecutor, Krister Petersson, will head the new inquiry.
About 10,000 people were quizzed following Olof Palme's murder in 1986; 134 people claimed to have shot him dead as he left a cinema with his wife.
The charismatic Social Democratic leader was left dying in a pool of blood on the pavement.
Mr Petersson faces a Herculean task: the Palme files take up 250m (820ft) of shelving.
The killing of Olof Palme
The investigator previously probed the 2003 murder of Sweden's Foreign Minister, Anna Lindh. He starts his new job in February, officials say.
Mr Petersson was quoted in the Swedish press as saying that his mission is to try and solve the murder and that he is optimistic of a breakthrough.
"I feel honoured and I accept the mission with a great amount of energy," he said in a statement. "It is an interesting and important task."
Mr Petersson also dealt with the trial of John Ausonius, who shot 11 immigrants in the 1990s - some of them using a laser sight, earning him the nickname of the "Laser Man".
Sweden is to re-open the investigation into the unsolved assassination of Prime Minister Olof Palme 30 years ago, officials say.