Thailand's Constitutional Court has dismissed Prime Minister Yingluck Shinawatra from office, ruling that she abused her power, deepening the kingdom's political uncertainty.
The judge who delivered the verdict said Ms Yingluck had abused her position by transferring the National Security Council chief to another post in 2011 so that a relative could benefit from subsequent job moves.
"The accused was involved in the transfer of Thawil Pliensri from his position as National Security Council head," the judge said, adding that it was done "in order for Priewpan Damapong, a relative of the accused, to gain a new position".
"The accused acted for her own political benefit ... The transfer wasn't done for the benefit of the country," he added.
Ms Yingluck denied wrongdoing.
Several cabinet ministers who endorsed the decision to transfer the security chief were also stripped of their status.
The Thai cabinet appointed a new caretaker prime minister shortly after Ms Yingluck was removed from office.
"The cabinet has agreed to appoint Niwattumrong Boonsongpaisan to act as caretaker prime minister," Phongthep Thepkanjana, a deputy prime minister said.
Ms Yingluck has faced six months of protests in the capital, Bangkok, aimed at toppling her government.
The anti-government protesters have failed to achieve their aim in the street but turned to legal challenges to remove her.
Some legal experts had expected her entire government to be forced out if she was found guilty.
It remains unclear how a new premier will be appointed.
In Thailand the prime minister is normally elected by the lower house of parliament but that was dissolved in December when Ms Yingluck called a snap election to try to defuse the protests.
From that point, she headed a caretaker administration with limited powers. The election in February was disrupted and later declared void by the Constitutional Court.
The crisis broadly pits Bangkok's middle class and royalist establishment against the mainly poor, rural supporters of Ms Yingluck and her brother former premier Thaksin Shinawatra, who was ousted by the military in 2006 and lives in exile abroad to avoid a jail sentence handed down in 2008 for abuse of power.
Ms Yingluck's supporters accuse the Constitutional Court of bias in frequently ruling against the government.
In 2008, the court forced two Thaksin-linked prime ministers from office.