The Queen inspects the Honour Guard as part of Canada Day celebrations on Parliament Hill in Ottawa. (Sean Kilpatrick/Canadian Press)

Queen Elizabeth told 100,000 people on Parliament Hill on Thursday that she could think of no better reason to celebrate than Canada's 143rd birthday.

The Queen was spending her first Canada Day in Ottawa since 1997.

At 84, the Queen said she has witnessed more than half of Canada's national history and praised what Canada stands for.

"This nation has dedicated itself to being a caring home for its own, a sanctuary for others and an example to the world," she said.

The monarch earned a roar of applause when she mentioned a Canadian moment of pride — the gold medal win for Canada's men's Olympic hockey team. The Queen also praised the commitment of the Canadian Forces, and said Canada has reason for optimism, even in trying times.

An estimated 100,000 party-goers packed Parliament Hill, compared with 35,000 last year.

Many of the thousands arrived before dawn to ensure a front-row seat to see, and perhaps meet, the Queen during her walkabout scheduled for later in the day.

The Queen arrives on Parliament Hill to celebrate the country's 143rd birthday. (CBC)

The Queen spent Wednesday night at her official residence in Canada, Rideau Hall, and then sat for an official portrait on Thursday morning.

With her personal Canadian flag flying from the Peace Tower, the Queen was honoured with a flypast by CF-18 jetfighters and another by the aerobatic Snowbirds, as well as a march-past by the Guard of Honour.

The Queen was serenaded by Canadian artists including Quebec pop star Isabelle Boulay, bagpipers the Campbell Brothers, the Barenaked Ladies and the Montreal Jubilation Gospel Choir.

She was also lauded by a host of luminaries, including Prime Minister Stephen Harper, actor Christopher Plummer and figure skater Joannie Rochette, who received a warm round of applause from the spectators, many decked out in red and white.

"Thank you for being there for me in my times of joy and sadness," said Rochette, who skated to a bronze medal in the Vancouver Olympics, just days after the sudden death of her mother.

"I had the sense that all of Canada was cheering us on," she said in French.

Canada Day celebrated abroad

In England, thousands of people flocked to Trafalgar Square in London for Canada Day.

Gov. Gen. Michaëlle Jean greets visitors during a ceremony at the Shanghai World Expo site on Canada Day. (Aly Song/Reuters)

"Every year we have had 30,000 to 50,000 people that come to the square over the course of the day," said Canadian High Commissioner James Wright. "It's a showcase of what's best about Canada."

The festivities opened with a performance by the Canadian Tenors and included street hockey competitions. Visitors got to meet Mounties and see a totem pole being carved.

Canadian wine, beer and Tim Hortons coffee were all on tap. Canadian music played all day, and the festivities will culminate in a huge concert in the evening. Visitors could also enjoy bison burgers.

Gov. Gen. Michaëlle Jean celebrated Canada Day far from home.

Jean was at the 2010 World Expo in Shanghai, China, where she made a speech, led a Maple Leaf flag-raising ceremony and enjoyed some beef from home at the Canadian pavilion.

Canadian troops in Afghanistan celebrated the nation's birthday by munching on hamburgers and hotdogs. Many wore red and white and listened to Bryan Adams tunes.