The president also said Belgium will return remains of the former prime minister, but did not give specifics.
The mausoleum will be built before the country celebrates its 61st independence anniversary in June 2021.
“On the sidelines of the celebration of the 61st anniversary of our independence, the country will show its gratitude to the Prime Minister Patrice Emery Lumumba, one of the national heroes whose relics will be repatriated and who will finally be given a tomb worthy of his sacrifice for the nation,” President Tshisekedi said.
Patrice Lumbumba was killed by a firing squad in January 1961. His body was never found and one of his teeth was believed to be kept in Brussels by one of the people who participated in his elimination.
A court in Belgium in September said that the tooth should be given to Mr Lumumba’s daughter, Juliana Lumumba, who had written a letter to the Belgian king asking for its return, according to the Brussels Times website.