The image, taken by Richard Murray from Waterlooville, Hampshire, UK, captures the night-time scene at Cowdray ruins in Midhurst, West Sussex, claiming the top prize in the contest.
The competition celebrates the national park’s status as one of only 20 International Dark Sky Reserves in the world, which recognises the region as one of the best places globally to stargaze.
South Downs lead ranger Dan Oakley said of the winning image: “It’s such a well-framed image and shows what the landscape would have been like a couple of centuries ago.
Mr. Murray said: “We were blessed with crystal clear skies and I was lucky enough to be able to capture this shot of the Milky Way rising behind the Cowdray ruins.
Runner-up in the main category was a shot of the moon rising behind Beachy Head lighthouse, near Eastbourne taken by Andrew Parker.