A specially-converted Ford Transit will be used in Aberdeen over the next year as part of the city's drive for better air quality and more sustainable transport options.
The city is among the only places in Scotland to have hydrogen fuel pumps, which are used by the world’s first double decker buses to run on the gas.
The test vehicle is slightly larger than a typical Royal Mail van, potentially making it suitable to support the company's growth in parcel deliveries.
Royal Mail said it will be the first time in ten years that a hydrogen-powered vehicle has been introduced into its fleet, and will be used to deliver letters, cards and parcels.
The van can travel up to 120 miles in dual fuel mode, with the vehicle also having a diesel engine.
It will generate 60 per cent of its power from hydrogen.
Royal Mail experimented with hydrogen vehicles in 2010 but said the technology had significantly evolved since and it was keen to see whether it was suitable for larger vehicles and longer routes, where electricity may not be viable fuel.
James Baker, chief engineer and fleet director at Royal Mail, said: "As a company we are committed to making changes to our operations that reduce our environmental impact.
"Hydrogen is viewed by many as a vital source of future sustainable energy so is a perfect addition to our programme of initiatives that enable us to assess ways of achieving this, while allowing us to continue to deliver letters and parcels safely, efficiently and responsibly."
Philip Bell, Aberdeen City Council's hydrogen spokesman, said: "We are absolutely delighted to support green transport technology in our city by providing Royal Mail with a hydrogen-powered van to operate from its Altens Mail Centre in Aberdeen for an initial 12-month trial period.
"Aberdeen is already a global leader in pioneering transport technologies and we at Aberdeen City Council have demonstrated our commitment to innovation by helping fund in partnership, the world's first hydrogen-powered double-decker buses.
"We are determined to meet our environmental obligations by tackling air pollution while also establishing the city as 'Centre for Excellence' for hydrogen."