A man who claimed to be a volunteer first-aider was on Monday given a four-year prison term and fined HK$5,000 over a protest in Causeway Bay in 2019.
The District Court had earlier found Chan Cho-ho guilty of rioting and possessing an unlicensed radio communication device during the incident on August 31, 2019.
In sentencing, Judge Frankie Yiu said the riot that took place on the day involved more than 300 people and lasted for around half an hour.
He noted that some Molotov cocktails had been thrown at the scene.
The judge said he did not believe that Chan, who is in his 20s, was there as a voluntary first-aider as he claimed.
Yiu said Chan had been wearing protest gear and tried to run away from the police, while a companion had attempted to attack officers.
The court earlier cleared six other defendants in the case of rioting.