A Bahraini court jailed six Shias for life and two for 15 years on Wednesday after convicting them of "spying" for Iran, a judicial source said.
The criminal court also stripped all eight of their citizenship, the source added.
The court also found them guilty of "joining a terrorist group, possessing arms, ammunition and explosives," and training in their use, the source said.
In recent weeks, Bahrain's Sunni rulers have carried out an intensifying crackdown against leading figures from the kingdom's Shia majority that has drawn criticism from the United Nations and the United States.
Manama has repeatedly accused Shia Iran of fanning persistent unrest among the the majority community since security forces crushed Shia-led protests for a constitutional monarchy and an elected prime minister in 2011.
Scores of Shias have been jailed on charges of involvement in the unrest.
Authorities have stripped at least 261 Bahrainis of their citizenship since 2012, according to the Bahrain Centre for Human Rights.
They include the kingdom's Shia spiritual leader, Sheikh Isa Qassim.
Activists have said that those left stateless are usually given a one-year passport and a travel ticket to a foreign country.