Hong Kong democracy activists Joshua Wong, Agnes Chow and Ivan Lam have been sentenced to jail for their involvement in mass protests last year.
The trio had been found guilty of unlawful assembly.
The pro-democracy movement has been stifled since Beijing introduced a controversial security law with harsh punishments.
But as the alleged offences took place before the law's enactment, the trio have avoided a potential life sentence.
Wong has received a sentence of 13 and a half months in jail, while Chow and Lam will be jailed for 10 and seven months respectively.
The trio were remanded in custody until today's sentencing, with Wong placed in solitary confinement.
All three were found guilty of organising and taking part in an unauthorised assembly near the police's headquarters at the start of the pro-democracy protests in June last year.
"The defendants called on protesters to besiege the headquarters and chanted slogans that undermine the police force," said Magistrate Wong Sze-lai, reported news outlet AFP.
"Immediate imprisonment is the only appropriate option."
Chow is said to have burst into tears when the sentence was read out. Meanwhile, Wong shouted "the days ahead will be tough but we will hang in there" as he was led away, according to reports.
Rights group Amnesty International condemned the ruling, saying it was a way for authorities to "send a warning to anyone who dares to openly criticise the government that they could be next".
"These three activists have been jailed in violation of their rights to freedom of expression and peaceful assembly," said Amnesty International's Asia-Pacific regional director Yamini Mishra.
"Their convictions should be overturned without delay and they must be released immediately and unconditionally."
Ahead of his sentencing, Wong had written a letter in jail, in which he said: "It's indeed hard to endure, but as many HK protesters face lawsuits/imprisonment like me, I hope you continue letting them know they are not alone... cages cannot lock up souls".
Who are the activists?
All three of them first rose to prominence as activists in the 2014 "Umbrella Movement" pro-democracy protests. Wong and Chow were still in their teens when they became student leaders.
One of the city's most recognisable dissidents, Wong has been a key figure in Hong Kong's pro-democracy efforts for years and has served several shorter prison sentences previously.
He also supported the new wave of protests that rocked the territory in 2019, which repeatedly led to violent clashes between demonstrators and police.
Beijing has since introduced a sweeping new security law for Hong Kong with harsh punishment for acts of secession, subversion and collusion with foreign forces.
In response, Wong disbanded his political organisation Demosisto, which he had co-founded with Chow. Lam was a chairman of the group.
Chow, who some have nicknamed the "goddess of democracy", was also arrested under the new security law in August this year but was released on bail. She faces separate charges of "inciting secession".
She has been named in the BBC's 100 Women list this year.
What is Hong Kong's new security law?
A former British colony, Hong Kong was handed back to China in 1997 but under the so-called "one country, two systems" principle.
It was supposed to guarantee certain freedoms for the territory - including freedom of assembly and speech, an independent judiciary and some democratic rights - which mainland China does not have.
But earlier this year, China passed a controversial, far-reaching national security law in the territory after years of pro-democracy and anti-Beijing protests, which reduced Hong Kong's autonomy and made it easier to punish demonstrators.
Beijing says the law will return stability to the territory, but western governments and human rights groups say it effectively curtails freedom of speech and protest.
After the law was introduced, a number of pro-democracy groups disbanded out of fears for their safety.