Thai authorities have banned former Prime Minister Yingluck Shinawatra from office for five years and launched a legal case that could see her jailed.
An army-appointed legislature impeached her over corruption in a scheme she oversaw to subsidise rice farmers.
The criminal charges, which also relate to the rice scheme, could result in a 10-year jail term.
The military has ruled Thailand since May 2014, when they overthrew Ms Yingluck's government in a coup.
The BBC's Jonathan Head in Bangkok says the impeachment sends a strong signal that there will be no compromise and her family will be removed from politics.
Ms Yingluck and her brother, tycoon and former Prime Minister Thaksin Shinawatra, remain hugely popular among Thailand's rural poor, but are hated by an urban and middle-class elite who accuse them of corruption and abuse of power.
Their party is the most popular in Thailand and has - under various different names - won every election since 2001.
Shortly after her impeachment, Ms Yingluck was due to hold a news conference at a Bangkok hotel.
But troops arrived and prevented her from speaking.
Thailand is still under martial law and unauthorised political meetings are banned.
Ms Yingluck has since posted a statement (in Thai) on her Facebook page accusing the authorities of trying to destroy her.
"Democracy has died in Thailand today, along with the rule of law," she said.
Analysis: Jonathan Head, BBC News, Bangkok
As they prepared for this vote, those advocating impeachment argued that it had nothing to do with politics or reconciliation, that it should be understood purely as a response to corruption in the Yingluck government's rice support scheme.
That there was corruption is undeniable; there is plenty of evidence. The generous subsidy was also financially unsustainable.
But no-one has yet been tried or convicted. Nor were Ms Yingluck's opponents able to explain how impeachment was possible against a politician who has already been removed from office, and by an assembly entirely appointed by the military.
So this was not about corruption, or the rule of law. It was the culmination of eight months of lobbying by hard-line opponents of the Shinawatra family, who want them purged from politics, and eight months of hesitation by military rulers who had some hopes of being seen as saviours, delivering the nation from political turmoil.
That calculation has now changed decisively. With a five-year ban from politics and a criminal charge hanging over her, Ms Yingluck faces the same fate as her brother - jail or exile.
Her party and supporters, who have relied on her family's funds, must decide whether they will seek new leadership or start resisting the military.
The allegations against Ms Yingluck centre on a scheme in which her Pheu Thai-led government bought rice from Thai farmers at a much higher price than on the global market.
It resulted in the accumulation of huge stockpiles of rice and hit Thailand's rice exports hard.
Anti-corruption investigators have accused Ms Yingluck and her party of using the scheme to buy votes from farmers, particularly from their power base in the north, and allowing government associates to profit from it.
On Friday, 190 out of 219 lawmakers present in the National Legislative Assembly voted to impeach her. Eighteen voted against impeachment while the others abstained. One lawmaker was absent for the vote.
The votes were written on a whiteboard as they were tallied, and broadcast on national television.
Ms Yingluck has maintained that she was not involved in the scheme's day-to-day operations, and has defended it as an attempt to support the rural poor. She has also said that she could not be impeached as she has not held a position in the government for months.
Her supporters say the claims against her are a ruse to remove her from politics.
Ms Yingluck also faces up to 10 years in prison if she is found guilty of negligence of duty, which the attorney general charged her with on Friday morning.
Surasak Threerattrakul, director-general of the Office of the Attorney General, said after considering all the witnesses and evidence from the National Anti-Corruption Committee "we agree that the case substantiates a criminal indictment charge against Yingluck".
- September 2006: Army ousts Thaksin Shinawatra
- December 2007: Pro-Thaksin party wins election
- August 2008: Mr Thaksin flees Thailand
- December 2008: Huge anti-Thaksin protests; court bans ruling party; Democrat's Abhisit Vejjajiva comes to power
- March-May 2010: Huge pro-Thaksin protests; dozens killed in army crackdown
- July 2011: Yingluck Shinawatra, sister of Mr Thaksin, elected PM
- November 2013: Anti-government protests begin
- May 2014: Ms Yingluck removed from office; military launches coup
- August 2014: Coup leader Prayuth Chan-ocha named PM by legislature hand-picked by military