The deal, which runs from today, includes more than 235 hours of programming a month and will span across the flagship Discovery Channel, as well as Discovery Science and Discovery History.
It was brokered by Michael Holt, the director of brand partnerships for Discovery Networks UK, and Henry Lewis, a sponsorship manager at OMD UK.
The partnership will include a fully integrated and cobranded microsite, two competitions promoted both on-air and on Discovery's social media channels, and an insertion into Discovery's newsletter.
Havas Worldwide has created a series of 80-second idents as part of the sponsorship.
These will play every hour as openers, closers and break bumpers, across Discovery programs such as 'Commander in Chief', 'Secret Service' and 'Endurance in the Wake of Shackleton'.
Mark Lynch, the marketing manager at Citroen's Fleet and Van, said: "Citroen is always looking for original ways to promote our LCV Range and reach a wider van-buying audience, including key small business owners.
"With this latest campaign, we have adopted a creative route. Havas Worldwide used characters that might be found in documentaries, to explore the features and benefits of the award-winning Citroen van models in a way that will catch the imagination of potential buyers."