Eastern Equatoria Assembly former Speaker Ambrose Emmanuel Ocholimoi died of hypertension on Tuesday at his resident in Torit town.
The state Spokesperson Clement Chichim Loku conveyed government condolence to the family and the state in general, Emmanuel Radio reported.
Mr Loku described the late Ocholimoi as full of energy and love for his country since the liberation struggle and during his services as a speaker.
He said the state lost a great man when it needed him most.
The spokesperson said Governor Louis Lobong Lojore declared three days of mourning and lowering of flags in the state.
The body of the late Ocholimoi on Tuesday was already in state Assembly for MPs to pay their last respect and memorial mass is expected on Wednesday before the burial.
The death of Ambrose Emmanuel Ocholimoi comes a year after that of Torit Central Constituency MP Marcelo Dominic Otwari.