Thousands of visitors each year walk along Hadrian's Wall, a UNESCO World Heritage Site that guarded the Roman Empire's northwestern frontier.
Many have paused to admire and photograph the tree at Sycamore Gap, a beloved icon of the landscape that was made famous when it appeared in Kevin Costner's 1991 film Robin Hood: Prince Of Thieves.
Photographs from the scene on early Thursday showed that the tree was cut down near the base of its trunk, with the rest of it lying on its side.
Northumbria Police said the teen was arrested on suspicion of causing criminal damage.
He was in police custody and assisting officers with their inquiries, the force said.
"The tree is a world-renowned landmark and the vandalism has caused understandable shock and anger throughout the local community and beyond," police said in a statement.
"This is an incredibly sad day," police superintendent Kevin Waring said.
"The tree was iconic to the North East and enjoyed by so many who live in or who have visited this region."
The Northumberland National Park authority asked the public not to visit the felled tree, which was voted English Tree of the Year in 2016.
Alison Hawkins, who was walking on the Hadrian's Wall path, was one of the first people who saw the damage early Thursday.
"It was a proper shock. It's basically the iconic picture that everyone wants to see," she said.
"You can forgive nature doing it but you can't forgive that."
