Having dubbed the Commonwealth the "original worldwide web", a monarch born soon after the age of steam has urged leaders of more than 50 nations to implement bold reforms that will keep their institution "fresh and fit for tomorrow".
The 85-year-old Queen appealed for vibrancy and renewal as she opened the Commonwealth Heads of Government Meeting (CHOGM) in Perth, the largest gathering of world leaders that Australia has hosted.
"This meeting is the perfect opportunity to find responses to today's crises and challenges," she told leaders representing one-third of humanity across six continents.
The last time Australia hosted a CHOGM, at Coolum in 2002, the world was still reeling from a new chapter of global terrorism.
"Almost a decade later we find ourselves confronting new challenges - insecurity and uncertainty in finance, food supply, climate change, trade and development," the Queen said.
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
"This meeting promises to bring new vibrancy to the Commonwealth."
Earlier, the Queen opened the meeting in Perth, where issues from human rights to succession to the British throne will be discussed.
Leaders were greeted with a traditional indigenous cleansing ceremony at the Perth Convention Centre by elders from the Noongar Aboriginal tribe ahead of a dance performance amid tight security.
The monarch said she was delighted to be in Perth "for a meeting that promises to bring new vibrancy to the Commonwealth".
"Ladies and gentlemen, it gives me great pleasure to declare open this 21st meeting of the Commonwealth Heads of Government Meeting," she added.
Most Commonwealth leaders are attending, although Indian Prime Minister Manmohan Singh pulled out without giving a reason while Britain's David Cameron is arriving later Friday after attending the eurozone debt crisis talks.
