Amid heavy security, the monarch officially opened the three-day summit during a lavish ceremony, saying she was delighted to be in Perth "for a meeting that promises to bring new vibrancy to the Commonwealth".
"I wish heads of government well in agreeing further reforms that respond boldly to the aspirations of today and that keep the Commonwealth fresh and fit for tomorrow," she said.
Now 85, the queen said she had attended many such meetings that had looked to the future with a sense of vision and practical action.
"The results of this meeting may be global in impact or simply touch a single individual even imperceptibly. But in every respect I trust the results will be positive and enduring," she said.
Reforming the Commonwealth as it struggles to remain relevant in the 21st century will be a key focus for the grouping, composed mainly of former British colonies and embracing two billion citizens.
Australian Prime Minister Julia Gillard, the host, told the gathering that it was vital for the organisation to move with the times.
"The world has changed, and a wise institution changes too," she said.
"So as the Commonwealth journeys towards its centenary, it is time for renewal.
"Let us make CHOGM 2011 memorable for answering this question. Memorable for being the meeting that gave the Commonwealth the direction it needed at a time of global uncertainty and risk."
Outside the summit venue, thousands of police were on city streets with the centre of Perth in virtual lockdown to deter potential terrorist threats and limit any protests by those wanting to emulate the global "Occupy" movement.
About 1,500 people marched in solidarity with the Occupy movement against corporate greed and the growing rich-poor divide, but it passed off peacefully.
The CHOGM Action Network, which organised the rally, is also concerned about alleged human rights violations in Commonwealth countries, accusing Sri Lankan President Mahendra Rajapakse and Rwandan leader Paul Kagame of war crimes.
Police have been given special powers to deal with any protests and can search people at will and ban known activists from entering special zones.
"I think the authorities in the lead up have undermined their commitment to support peaceful demonstrations through intimidation. The repression has been intense," Colleen Bolger, a spokesperson for CHOGM Action Network told AFP.
Most Commonwealth leaders are attending the summit, although Indian Prime Minister Manmohan Singh pulled out without giving a reason and New Zealand's John Key is absent.
Commonwealth Secretary General Kamalesh Sharma said the meeting would consider a series of proposals, including establishing an independent commissioner to monitor human rights.
Foreign ministers have already agreed to adopt proposals from a Commonwealth Ministerial Action Group that will see governments in danger of violating human rights and the rule of law face earlier intervention by the bloc.
Leaders will also discuss proposals to change the rules for the line of succession to the British throne, with the subject taking on new momentum since the marriage of Prince William to Kate Middleton in April.
Other issues set to be discussed are the laws in many Commonwealth countries that criminalise homosexual sex and the prevalence of forced marriages of young girls.
COMMENTS (5)
Comments are moderated and generally will be posted if they are on-topic and not abusive.
For more information, please see our Comments FAQ
Will there be any valueable outcome of this show?
It seems as if:
Queen saying: Remember we ruled over you?
Delegates saying: Yes we remember we were your slaves..
@Paras Vikmani, Me neither.
@ Ali Tanoli
Improve your English. I didn't get you.
Why has our PM not visited it? I think even he considers it as irrelevant.