David Sewell, 37, of Valley Road, Grantham, England, pleaded guilty to the charges which included rape and sexual assault on nine boys aged between seven and 15.
Judge Michael Heath at Lincoln Crown Court described his crimes as an "appalling litany of sexual assaults on young boys".
He sentenced Sewell to 18 years in prison.
The court heard Sewell met some of his victims through the scout movement. The offences were carried out between 2004 and his arrest this year when a victim came forward.
The charges Sewell faced were of engaging in sexual activity in the presence of a child under 13, two counts of sexual assault of a boy by touching, two counts of causing a child under 13 to watch or look at images of sexual activity, two counts of raping a boy under 13 and one count of voyeurism.
During sentencing, Judge Heath said "For your sexual gratification, you systematically and gratuitously abused no fewer than 11 boys in a sordid and disturbing manner.
"You met those boys in your capacity as a scout master of long standing. Their parents trusted you with their sons and you gravely breached their trust.
"Across the length and breadth of this country, there are men and women of impeccable character who will be appalled at your behaviour and will feel terribly let down and worried that what you did will somehow reflect on and besmirch their good names."
Det Supt Rik Hatton, from Lincolnshire Police, commended the first victim for coming forward and said the abuse had had a "horrific effect" on the victims and their families. "It was really brave of that victim to come forward and tell us his experiences," he said.
"From that our investigative team were able to piece together a pattern of his [Sewell's] offending history.
"It is quite clear that Sewell is a really dangerous predatory paedophile and the way paedophiles work is in grooming their victims, getting them into a position of trust and allowing themselves access to them."
The Scout Association said Sewell had been subject to a CRB check before starting but he had not been charged with any offences at the time.
A spokesman said members "condemned the actions of Sewell" and were pleased he had been "suitably punished".
Please pray for these 11 victims, and for Sewell, that they will be restored to a normal life. Pray that the children can forgive and move on. Pray that the enemy will not be allowed to use the abuse as an entry to destroy the kids' lives. Please pray our 3:15 PM prayer every day.