The accident happened at around 9:00pm along the Ntungamo-Mbarara Road in Itojo, Ntungamo district.
Rwizi regional Police Spokesman Samson Kasasira says Aponye's Land Cruiser number UBF 300Z rammed into a stationary FUSO truck registered as UAZ 767D, which had encountered a mechanical problem and was parked alongside the road.
The tycoon died on spot.
Kasasira says his body was commuted to the mortuary at Itojo Hospital, while two other casualties were rushed to Mbarara Regional Referral Hospital fore medical attention.
Aponye was the chairman of the ruling National Resistance Movement party (NRM) in Rukiga district.
As one of the wealthiest people in the country, Aponye owned several properties under his company Aponye Uganda Ltd.
Some of his assets in the city include Aponye Mall in down town Kampala, Aponye Mall Ntinda, Aponye Hotel on William Street and Mega Standard Supermarket on Burton Street.