Judge Dame Victoria Sharp told the EDL founder that the time he previously spent behind bars for the contempt will be taken into account, reducing his sentence to 19 weeks – of which he will serve half before being released.
Robinson, whose real name is Stephen Yaxley-Lennon, was last week found to have committed contempt of court over a video he broadcast on Facebook which featured defendants in a criminal trial.
“We are in no doubt a custodial threshold is passed in this case,” said Dame Victoria on Thursday. “Nothing less than a custodial penalty would reflect the gravity of the conduct.”
His supporters erupted in anger outside following the sentencing verdict. The crowd chanted “we want Tommy out” before some hurled bottles and cans at police.
Posts by the Tommy Robinson News account on messaging app Telegram said: “Time for the protests to start, this is an absolute joke!”
Robinson had earlier turned up at the Old Bailey with far-right agitator Katie Hopkins amid chaotic scenes, mobbed by fans as he made his way towards the court. He showed little emotion as he was led down to the cells after the verdict.
High Court judges found Robinson was in contempt in three respects when he filmed men accused of the sexual exploitation of young girls and live-streamed the footage on Facebook, in breach of a reporting ban, outside Leeds Crown Court in May 2018.
Dame Victoria said Robinson had encouraged “vigilante action” in the video, which lasted an hour-and-a-half and was viewed online 250,000 times on the morning of the broadcast.
The words he used in the video would have been understood by viewers as “an incitement” to harass the defendants and “gave rise to a real risk the course of justice would be seriously impeded”, the judge said.
Dame Victoria also said Robinson had displayed “reckless disobedience of an important court order”.
The judged added: “The respondent cannot be given credit for pleading guilty. He has lied about a number of matters and sought to portray himself as the victim of unfairness and oppression.
“This does not increase his sentence, but it does mean that there can be no reduction for an admission of guilt.”
Robinson was originally jailed for 13 months after being found in contempt of court on the day of the broadcast.
He served 10 weeks in jail before being freed after the original finding of contempt was overturned by the Court of Appeal in August 2018.
But the case was then referred back to the Attorney General, who announced in March that it was in the public interest to bring fresh proceedings against Robinson.
Dame Victoria and Mr Justice Warby gave permission for the Attorney General to bring a new case against Robinson at a hearing in May.
On Thursday he received six months for filming defendants in a criminal trial and broadcasting the footage on social media, and three months for an earlier contempt finding.