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Judge Rose told the footballer, who played 12 times for England, there had been "an abuse of trust - you are trusted by young fans to behave properly".
He said: "She had only just turned 15 when you began grooming her, because, as you were to admit, you found her sexually attractive."
The judge told Johnson the offences happened "at a time when you were engaged in frequent sexual intercourse with multiple partners".
At the start of his trial last month, Johnson had admitted grooming the girl and one charge of sexual activity, relating to kissing her. He was found guilty of sexual touching and cleared of one charge relating to another sexual act.
Judge Rose said Johnson had had "every opportunity" to enter guilty pleas to the charges he finally admitted. He ordered the footballer to pay £50,000 of the prosecution's £67,132 costs.
During the three-week trial the jury heard the former winger met the girl after agreeing to sign football shirts for her.
He admitted kissing the teenager but told the jury an encounter in his Range Rover "went no further".
The girl told the court he had "put his hands down her pants" and she performed a sex act on him.
The jury cleared Johnson over the sex act claim but convicted him by a 10-2 majority on the sexual touching charge.
Restrictions have now been lifted that prevented it being reported that, when Johnson was arrested, police found medicines in a safe indicating he may have been suffering from sexually transmitted infections.
In a victim impact statement read to court, the girl said she had been forced to endure thousands of malicious and slanderous remarks on social media and had been approached by a stranger asking about her relationship with the footballer.
She felt at risk going out and her schoolwork had suffered "massively", the court was told.
"I have entered many dark places over this 12-month period," she said.
"Ultimately, it was like I was being taunted as if to say he could do what he wants and get away with it."
In another statement to the court, her mother said there "had been no winners" and defended the decision to report the matter to police in order to "protect other vulnerable children".
She stressed the family had never sought financial gain.
Earlier, Dr Philip Hopley, a consultant psychiatrist giving evidence for the defence, told the court: "This is a man who, at the age of 28, is socially and psychologically immature."
The doctor said he found no evidence in Johnson of an attraction to pre-pubescent children or "sexual perversion".
Speaking after Johnson was sentenced, Det Insp Aelfwynn Sampson, of Durham Police, said: "Fame, celebrity and a position of power does not give you the right to break the law in pursuit of whatever you desire.
"This girl should have been safe but she was used by the public figure she looked up to most."
Jon Brown, from children's charity the NSPCC, questioned whether the Football Association's "really comprehensive high quality rules and regulations and policies" for child protection were followed throughout the game's hierarchy.
"We are concerned about the extent to which they're actually being embedded and implemented at club level," he said.
"We're concerned that may not be the case right across the country."
Outside the court, Gerry Wareham from the Crown Prosecution Service, said: "Adam Johnson exploited a young star-struck fan, actively grooming her over a number of months in single-minded pursuit of his own sexual gratification."
Earlier, the court was told the player had lodged an appeal against his conviction for sexual activity with the girl.
Johnson began his career at Middlesbrough before moving to Manchester City and then on to Sunderland in 2012.