Nguyen Ngoc Nhu Quynh, also known as "Mother Mushroom," was sentenced at the end of a one-day trial in the south- central province of Khanh Hoa, lawyer Vo An Don said.
Her conviction related to the content of 18 articles on her Facebook page and interviews with foreign news outlets such as Voice of America and Radio Free Asia, Don said.
Quynh, 37, co-founded a network of bloggers and is very popular in Vietnam. She has written about human rights, civilian deaths in police custody and the release of toxic chemicals by a Taiwanese-owned factory that killed thousands of fish in one of Vietnam's worst environmental disasters.
"Nguyen Ngoc Nhu Quynh did not admit that she committed any crime, saying she has a right to freedom of expression," Don said.
Also Read
Don said the sentence was "too harsh and unjust" and that Quynh plans to appeal the verdict.
Quynh was arrested in October when she was visiting a fellow activist in prison.
International human rights groups including Human Rights Watch, Amnesty International and Sweden-based Civil Rights Defenders have called for her immediate release.
"The scandal here is not what Mother Mushroom said, but Hanoi's stubborn refusal to repeal draconian, rights-abusing laws that punish peaceful dissent and tarnish Vietnam's international reputation," said Phil Robertson, Human Rights Watch's deputy Asia director.
Responding to the calls for the blogger's release, Foreign Ministry spokeswoman Le Thi Thu Hang said Quynh's trial was held in accordance with Vietnamese law.
"Like other countries in the world, in Vietnam, all law- violating acts must be strictly dealt with in accordance with the regulations of Vietnamese law," Hang said at a regular news briefing.
In March, Quynh received the International Women of Courage Award from the US State Department. Vietnam said the award "was not appropriate and of no benefit to the development of the relations between the two countries."
According to Human Rights Watch, there are about 110 known political prisoners in Vietnam.
Vietnam denies it holds any political prisoners, saying only those who break the law are put behind bars.
Disclaimer: No Business Standard Journalist was involved in creation of this content