Galloway, known in Parliamentary circles as "Gorgeous George" incurred the wrath of Tony Blair when he compared the British prime minister and US President George Bush to wolves.
He drew the comparison at an anti-war meeting and said at another that British soldiers were lions led by donkeys.
Galloway, member of parliament for Glasgow in Scotland, confirmed his expulsion as he emerged from a party hearing in London on Thursday and angrily condemned the tribunal as a "kangaroo court".
Most of the charges stemmed from an interview the left-wing firebrand gave to Abu Dhabi Television in March 2003.
"I want to apologise to the wolf. Mr Bush and Mr Blair are a jackal and a jackass. I will ensure Mr Blair regrets this day"
George Galloway, MP
The life-long socialist had been accused by the Labour Party of inciting Arabs to fight coalition troops during the Iraq war and encouraging British troops to disobey what he called "illegal orders."
He was one of Britain's most outspoken and controversial critics of the war in Iraq but had the support of millions across the UK including a huge section of the Muslim community.
Despite the fact Galloway protested vigorously on the steps of the Iraqi embassy in London when the UK sold arms to Saddam Hussein in the 70s, his critics called him an apologist for the regime because of his visits to Iraq.
Galloway, sometimes nicknamed the MP for Baghdad Central, started libel proceedings in June against Britain's Daily Telegraph newspaper after it reported he had been in the pay of the Iraqi government.
American newspaper The Christian Science Monitor retracted a similar story alleging Galloway received $10 million to boost Iraq's reputation in the West and published an apology.
Blair's decision to go to war provoked widespread resistance in Britain and his popularity has since slumped.
An unrepentant Galloway said: "Mr Blair's response to the disaster of the war is to attack those who stood against the war and to root them out of British politics."
"It was a travesty of justice ... a politically motivated kangaroo court whose verdict clearly had been written in advance in the best tradition of show trials," said Galloway.
He complained: "I was found guilty by unanimous verdict and I've just been informed that after 36 years of membership I have been expelled forthwith."
Galloway is often referred to
as the MP for Baghdad Central
Galloway said, "I intend to defend my seat in parliament."
If he decides to stand as an independent candidate, it would be an embarrassment for Blair as it would be seen as a mini-referendum on the Iraq war.
And he was defiant to the end, telling reporters: "I want to apologise to the wolf. Mr Bush and Mr Blair are a jackal and a jackass. I will ensure Mr Blair regrets this day."
Expulsions from political parties are relatively rare events in Britain.
The last time an MP was formally expelled from the Labour Party was in 1998 when London Mayor Ken Livingstone was automatically thrown out of the party for standing against an official Labour candidate at the mayoral elections in 2002.