Dyfed Powys Police said that a man in his 30s had died at the scene after a silver Ford Transit had crashed on the B4569, in Mid Wales.
The crash took place between Caersws and Trefeglwys at around 10.30pm yesterday with the road closed for more than 12 hours following the incident.
Police said they believe the van was travelling westbound towards Trefeglwys.
Officers said they are investigating the cause of the crash and next of kin have been told
They have also appealed for anyone with information to come forward.
People with information can contact officers online, by emailing firstname.lastname@example.org, or by calling 101.
Those who are deaf, hard of hearing, or speech impaired can text the non-emergency number on 07811 311 908.