A tramper has been rescued after spending a freezing night in Marlborough bush.

The 25-year-old man injured his ankle while on a day tramp up Mt Riley in Mt Richmond Forest Park.

He managed to find a spot with cellphone coverage and called his friends for help.

His friends relayed his location to police at 8.20pm yesterday.

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Blenheim police deployed two land search and rescue teams, who found the man about 4am today.

Police said he was wearing light clothing, was wet and cold and had a small amount of food and water.

He was given food and dry clothing before they began the trek down the mountain.

Police commended search volunteers for their hard work through the night in "freezing conditions".

"Police would also like to take the opportunity to remind people who are using the outdoors at this time of year to make sure they are adequately prepared with warm clothing, food and water," police said.