Pauline Hanson, the controversial founder of Australia's anti-immigration One Nation party, has been sentenced to three years in jail for electoral fraud.
Both Hanson and Ettridge have been given three-year jail terms
Earlier on Wednesday, a court in Brisbane, Queensland, found her guilty of dishonestly obtaining electoral funds, and fraudulently registering her party in 1997.
One Nation's deputy director, David Ettridge, was also given a three-year jail term.
Hanson's reaction to the guilty verdict was typically theatrical, says BBC correspondent Phil Mercer.
This red-haired, hard-edged, twice-divorced mother of four shook the political establishment, provoked outrage, and inspired a legion of satirists
"Rubbish, I'm not guilty ... it's a joke," she shouted, clearly shocked.
It took the 12-person jury just nine hours to decide on the guilty verdict.
Hanson was found guilty of illegally using the names of 500 members of a support group to register One Nation as a political party, as well as fraudulently obtaining almost A$500,000 (US$325,000) in electoral funds.
Chief Judge Patsy Wolfe said the pair had undermined confidence in the political process.
Hanson's lawyer has said she will appeal against both the conviction and the jail sentence.
Queensland Premier Peter Beattie urged Hanson's supporters to accept the court's decision.
"There will be people who will see her as being martyred. I just say to all those people who think that way, that this
process has been followed in accordance with the law," he said.
But fans of the right-wing maverick were quick to show their anger at the verdict.
"I think there were certain major influences in the political area. They wanted to make sure she didn't come back to haunt them," One Nation state parliamentarian Bill Flynn told ABC radio.
Pauline Hanson's conviction will almost certainly bring to an end one of Australia's most controversial political careers, our correspondent says.
Hanson, a former chip shop owner, shot to national and international attention in the late 1990s with her extreme views on immigration, Australia's indigenous people and asylum seekers.
She claimed that Australia would be overrun by Asian migrants, that Aborigines received unfair benefit payments not available to others and that asylum seekers were common criminals and queue jumpers.
She won a seat in Australia's federal parliament as an independent candidate in 1996, and in 1998 her party won almost a quarter of the vote in Queensland's state election.
The party began to disintegrate in the run-up to 2001 federal elections, in which it failed to secure any seats after Prime Minister John Howard's Liberal party moved to the right on immigration issues.
But despite her party's decline, Hanson is still able to arouse passions across the Australian political divide.
Her supporters see this twice-divorced mother of four as an inspirational leader, fighting for the rights of ordinary Australians, our correspondent says.
Her opponents, he says, simply see her as a racist.