Chief Executive Carrie Lam says her management of an extradition bill caused "disputes in society." Protesters say they want the bill scrapped and Lam to step down.
A judge sentenced the leaders of the protests to up to 16 months in prison. Rights groups said the sentencing would have a chilling effect on future demonstrations in Hong Kong.
The rallies were spurred by outrage in Hong Kong over the Chinese government's plans to limit voters' choices among candidates to lead the city's government.
Joshua Wong was the 17-year-old face of massive pro-democracy protests in the semiautonomous city. Now, he and two others have been given stricter sentences that bar them from office for five years.
Joshua Wong and Nathan Law were given community service for their part in massive democracy protests two years ago. Jail time for Alex Chow is being suspended so he can pursue graduate studies abroad.