Two people were killed and nine were seriously wounded in the shooting at three locations, chiefly outside the London Pub, a popular gay bar, on June 25, 2022.
The Oslo District Court said Zaniar shot 10 rounds with a machine gun and eight shots with a handgun into the crowd.
It said Matapour had sworn allegiance to the Islamic State group and "has been radicalised for several years".
The 30-year sentence announced on Thursday was the highest penalty in Norway since terrorism legislation was changed in 2015.
Matapour can request parole after 20 years but can only be released if he is deemed no longer dangerous.
Prosecutor Aud Kinsarvik Gravås called it "the right outcome" and "a historically severe punishment".
The shooting shocked Norway and was among a number of "lone wolf" attacks in recent decades. (AP PHOTO)
Matapour's lawyer, Marius Dietrichson, said it was "a severe punishment" and they have not yet decided whether to appeal.
Espen Evjenth, who was hit by a bullet in the forehead at the London Pub, told the Norwegian news agency NTB that it was "a great relief".
Extensive video material of the attack had been presented in court.
The verdict was not read in court but sent out electronically.
Matapour was overpowered by bystanders after the attack and arrested.
Following the attack, a Pride parade was cancelled, with police saying they could not guarantee security.
The shooting shocked Norway, which has a relatively low crime rate but has experienced a series of "lone wolf" attacks by individuals in recent decades, including one of the worst mass shootings in Europe.
In 2011, a right-wing extremist killed 69 people on the island of Utoya after setting off a bomb in Oslo that left eight dead.
Six days before the attack, Norway's external intelligence agency, E-Tjenesten, learned from an undercover agent that a possible action was expected in a Nordic country and the information was passed to the domestic security service.
Matapour had pleaded not guilty.
He was examined by a court-appointed psychiatrist who concluded that he was sane at the time of the attack.
During the trial, both the prosecution and the defence agreed that Matapour fired into the crowd and there was no disagreement that the shooting was motivated by terrorism.
However, Dietrichson had sought acquittal, saying his client had been provoked to carry out the attack by an E-Tjenesten agent who was pretending to be a high-ranking member of the Islamic State group.
The court said "it is clear that the actions of the E-Tjenesten did not involve any illegal provocation" and "did not provoke an act of terrorism that would not otherwise have been committed".
The trial started in March and ended on May 16.
12°C