Hassan Isa was a senior member of the main Shiite opposition Al-Wefaq group, which was dissolved last year. The other 10 received sentences ranging from 10 years to life imprisonment.
The Bahraini al-Wasat news website said the case involves 24 defendants charged with establishing a terror cell that killed members of the police and was involved in other acts of violence. The group was also found guilty of harboring fugitives, among other charges.
Al-Wasat earlier reported that nine were stripped of their nationality.
Sunni-led Bahrain has jailed thousands of anti-government Shiite protesters accused of violence and terrorism. Dozens have been ordered stripped of their nationality.
The tiny island-nation, home to the US Navy's 5th Fleet, was rocked by Arab Spring-inspired protests in 2011 and has continued to see low-level violence amid a government crackdown.
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