Gay marriage supporters marched through central Perth this afternoon calling for the right towed under Australian law.
The rally, attended by more than 200 people, was part of a national day of protest calling for changes to the laws.
In Perth the protest was largely peaceful despite one confrontation when angry words were exchanged between marchers and a member of the public in the Hay Street Mall.
Protest co-convener Sam Cavallaro said people were calling for equal treatment.
"The ban on (same-sex)marriage is an affront to LGBTI rights and the ban is specifically there as a homophobic ban," he said.
He said formerprime ministerJohn Howard's 2004 amendment to the marriage act had specifically defined marriage as between a man and a woman and essentially functioned as a ban on same-sex marriage.
The majority of Australians support marriage equality, he said.
In an address, WA GreensMLC Lynn MacLaren called for the leaders of both major political groups to allow their members a conscious vote on any bill supporting gay marriage.
She said the current laws contravened Australia's obligations under the Universal Declaration of Human Rights.
Popular comedian Hannah Gadsby, Adam Hill's offsider on ABC show Gordon Street Tonight, also addressed the crowd and said she didn't understand the arguments against gay marriage.
She said prominent anti-gay marriage commentator Margaret Court was brave as a (now retired) sportswoman to speak out against same-sex attraction.
"It's like a truck driver speaking out against pies," she said.
No counter-protestors attended the rally.
Simultaneous rallies were held in Melbourne, Sydney, Brisbane, Canberra, Adelaide and Hobart to celebrate the Marriage Equality National Day of Action.
Thousands gathered outside the state library in Melbourne, waving banners and cheering as a host of guest speakers spoke of the need for legislative change.
Greens deputy leader and federal Melbourne MP Adam Bandt received a rock star's ovation when he took the microphone.
Mr Bandt, who has tabled a bill in parliament on the issue, pointed to US President Barack Obama's public declaration of support for same-sex marriage this week as a sign that the world's attitude was slowly shifting.
"If it's good enough for the leader of the free world, it should be good enough for the leaders of the political parties in Australia," Mr Bandt said.
TV host Charlie Pickering said future Australians would look back on the current rights of gay and lesbian couples with shame.
"If civil unions are enough (for same sex couples), then why don't we just ban marriage altogether?" he said.
Placards in the crowd shared slogans such as "what the world needs now is equal love", and "divorce discrimination".
Carl Katter, the gay half-brother of outspoken Queensland conservative MP Bob Katter, urged those at the rally to lobby their local politicians to bring about change.
"Tony and Julia, are you listening?" he shouted.
Actor and comedian Magda Szubanski, who recently came out as lesbian on national television, said politicians would soon become irrelevant as the push for change would overwhelm them.
"This movement, what we are about, is the forces of love, the forces of tolerance, the forces of a mature society that can accept difference and learn to live together," she said.
"Those forces are gathering across the globe."
In Brisbane, co-convener of pro-gay marriage group Equal Love, Jessica Payne, says the amount of people who turned up to support the rally was testament to how much support the movement had.
"If one of the world's most powerful people (Mr Obama) is supporting gay marriage, then it just shows how backwards Julia Gillard and the government is," she told the rally to thunderous applause.
As the US President announced his unequivocal support for gay marriage in the lead-up to the US presidential elections, Ms Gillard reaffirmed her opposition to gay marriage.
Marriage equality supporters in Brisbane also heard from rock group Faker's openly gay lead singer Nathan Hudson.
Hudson told the crowd that while he was not sure he ever wanted to marry, it was important he had a choice.
"I'm a human being and that's all that should matter," he said.
In Sydney this afternoon protesters carried rainbow flags and placards saying "Smash homophobia" as they marched on Taylor Square.
Crowds gathered at Town Hall in the Sydney CBD before travelling up Oxford Street - the home of gay night spots like the Stonewall Club - carrying signs with message such as "Marriage is about love and not gender".
Federal Greens senator Lee Rhiannon called for the ALP caucus to bind on same-sex marriage rather than allow conscience votes.
"We would have the numbers if Labor were obliged to follow their own policy. Remember that policy is now same-sex marriage," Senator Rhiannon said.
Katherine Hudson, the founder of advocacy organisation Wear It Purple, addressed the crowd wearing a T-shirt bearing the words "Marriage equality: its time".
Ms Hudson compared same-sex marriage with the abolition of slavery, the fight for women's rights and the recognition of indigenous people.
"Today we fight to correct another injustice," she said. "Change doesn't happen without a struggle."
Ms Hudson said Labor figures including NSW Opposition Leader John Robertson, Senator John Faulkner and federal Finance Minister Penny Wong were prominent advocates for gay rights while federal Opposition Leader Tony Abbott was "conspiratorially homophobic".
Some motorists honked their support while other passers-by expressed disapproval. One told AAP: "They should just live their lives quietly."