Axel Rudakubana has been jailed for a minimum of 52 years for the murders of three girls at a dance class in Southport.
The 18-year-old was sentenced in his absence at Liverpool Crown Court after indicating he would be "disruptive" if he was present in the courtroom.
Rudakubana of Banks, Lancashire, pleaded guilty to all 16 offences he faced on the first day of his trial at Liverpool Crown Court on Monday.
Alice da Silva Aguiar, nine, Bebe King, six, and Elsie Dot Stancombe, seven, all died following the attack at the Taylor Swift-themed class in The Hart Space on a small business park in the seaside town shortly before midday on 29 July last year.
The defendant admitted their murders as well as the attempted murders of eight other children, who cannot be named for legal reasons, as well as class instructor Leanne Lucas and businessman John Hayes.
Rudakubana was not expected to receive a whole life order because he was 17 at the time of the attack.
The measures can normally only be imposed on criminals aged 21 or over, and are usually only considered for those aged 18 to 20 in exceptional circumstances.
Judge Julian Goose said: "Had he been 18, I make it clear I would have been compelled to impose on him life imprisonment without a minimum term.
"However, the law does not permit such a sentence for those offenders who are under 18 when they offend."
He said the minimum term he would fix would be "very substantial" and added: "I consider at this time it's likely he will never be released and will be in custody for all his life."
He said that Rudakubana must serve a minimum of 52 years in detention for his "extreme violence".
"The harm Rudakubana has caused to each family, each child and to the community has been profound and permanent," he added.
The judge said that the attack itself took just 15 minutes.
"Had he been able to, he would have killed each and every child -- all 26 of them," the judge said.
"He was prevented from murdering more only by the escape of other children."
After some of the injured girls escaped, Rudakubana "returned to continue his sustained and brutal violence against two of the youngest of those children, stabbing them multiple times," the judge added.
Rudakubana further pleaded guilty to possessing a knife on the date of the killings, which he bought off Amazon, production of a biological toxin, ricin, on or before 29 July, and possession of information likely to be useful to a person committing or preparing to commit an act of terrorism.
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The terrorism offence relates to a PDF file entitled 'Military Studies In The Jihad Against The Tyrants, The al-Qaeda Training Manual', which he is said to have possessed between 29 August 2021 and 30 July 2024.
The ricin, a deadly poison, and the document were found during searches of the home in Old School Close which he shared with his parents, who are originally from Rwanda.
Documents about Nazi Germany, the Rwandan genocide and car bombs were found on Rudakubana's devices during police searches of his home.
UK Prime Minister Keir Starmer told the families of three girls murdered that "we stand with you in your grief".
He added that Axel Rudakubana had been responsible for "one of the most harrowing moments in our country's history".
Within minutes of Axel Rudakubana being jailed, law officers announced they had received a request to consider whether the 52-year minimum term was too short.
The Attorney General's office said the case was referred under the unduly lenient sentence scheme - just one request is needed for it to be considered.
The law officers - Attorney General Lord Hermer and Solicitor General Lucy Rigby - have 28 days to decide whether to refer the sentence to the Court of Appeal.
There is a high threshold for a successful reference under the scheme - the sentence must be deemed to be not just lenient but unduly so, for example if the judge has made an error or imposed a sentence outside the usual range associated with the circumstances of an offence.
Even then, the Court of Appeal may decide to refuse to review the case or uphold the existing sentence.
Mr Starmer addressed the nation on Tuesday to say Britain faces a new threat of terrorism from "extreme violence carried out by loners, misfits, young men in their bedrooms" following the Southport murders.
Home Secretary Yvette Cooper announced an inquiry into the case following Rudakubana's guilty pleas, including how he "came to be so dangerous" and why Prevent - a government body aimed at stopping people becoming terrorists or supporting terrorism - "failed to identify the terrible risk" he posed to others.
Despite a previous conviction for violence, at the age of 17 he was able to order a kitchen knife from Amazon which he used to fatally stab the girls, and Ms Cooper said the Government will "bring in stronger measures to tackle knife sales online in the Crime and Policing Bill this spring."
Unrest erupted across the country in the wake of the Southport attack, with mosques and hotels used for asylum seekers among the locations targeted.
In the hours after the stabbing, information spread online which claimed the suspect was an asylum seeker who had arrived in the UK on a small boat.
The day after the attack, thousands turned out for a peaceful vigil in Southport, but later a separate protest outside a mosque in the town became violent, with missiles thrown at police and vans set on fire.
More than 1,000 arrests linked to disorder across the country have been made since the attack, and hundreds have been charged and jailed.
Additional reporting by AFP
