It is the largest national security case in the city under a Chinese law that, in the wake of massive anti-government demonstrations in 2019, has virtually eliminated public criticism.
Former MPs Leung Kwok-hung, Lam Cheuk-ting, Helena Wong, and Raymond Chan are among those convicted.
They could now be sentenced to life in jail; a later date for sentencing is anticipated.
Nonetheless, the three judges chosen by the government to hear the case cleared former district council members Lee Yue-shun and Lawrence Lau.
Thirty-one of the 47 democracy advocates who were charged in 2021 for their participation in an unauthorized primary election entered a guilty plea.
Spectators predicted ahead of the court that their subversion case would show how the security statute is being abused to silence political dissent.
However, the governments of Beijing and Hong Kong maintain that judicial independence is being upheld and that the law has contributed to the restoration of stability in the city.
The US and other countries have denounced the trial as politically motivated and have called for the immediate release of those who are accused—many of whom have been detained since February 28, 2021.