Syed Ali attacked the teenager in Sunderland's Mowbray Park on 8 December last year.
Ali, from the city's Barnes area, was found guilty after a trial at Newcastle Crown Court.
Det Insp Phil Bond said Ali had "preyed on his victim, befriending her and quickly gaining her trust before subjecting her to a horrific attack".
He said: "I hope the victim and her family can now move on from what has been an incredibly distressing time and can come to terms with what has happened and rebuild their lives.
"Although we know this sentence will in no way help erase what has happened, we hope there is some comfort in knowing Ali is now in prison."

Brunon Kwiecien, 48, was convicted of planning a terrorist attack, illegal weapons possession and inciting two students to carry out an attack.
He suggested he had been manipulated by Polish intelligence agents.
Kwiecien was said to be fascinated with Norwegian mass killer Anders Behring Breivik.
Right-wing extremist Breivik killed 77 people in a bombing and shooting rampage in Norway in July 2011.
Kwiecien, a former professor at Krakow's University of Agriculture, was arrested in 2012.
Investigators believe he wanted to target parliament with four tonnes of explosives while then-President Bronislaw Komorowski and former Prime Minister Donald Tusk were due to attend, the trial heard.
"If Brunon Kwiecien hadn't been stopped, we would be talking amid the ruins of the state today," said judge Aleksandra Almert, according to the AFP agency.
While admitting he planned to carry out the attack, he also said he was subject to "provocation" by the intelligence services.
Kwiecien is the first Pole to be accused of terrorism, Polish media reported. He has no known links to established extremist groups.
A 47-year-old man who raped a 16-year-old girl in a Wearside park has been jailed for eight years.
[NEXT_CONCEPT]
A Polish university lecturer has been sentenced to 13 years in jail for plotting to ram a car packed with explosives into parliament.