Governments around the world subsequently had to pump trillions into their financial systems through bank bail-outs, central bank actions and huge stimulus plans to save their economies from collapse.
BBC business editor Robert Peston said that Lehman's collapse had huge repercussions on the psyche of investors and the scale of the financial crisis.
"The significance of Lehman Brothers was in the massive panic that it caused in the marketplace, where funds were withdrawn from any bank anywhere in the world that was perceived as remotely vulnerable," Robert Peston said.
"That was the moment people thought, crikey, we're on the verge of a depression."
Most economists now think the world has avoided a second Great Depression, that some thought possible a year ago.
Bob Diamond, CEO Barclays Capital: 'Some valuable lessons have been learned'
But there is now concern that as the banks start to recover, they have not taken the necessary steps to prevent a repeat of the crisis.
"Alarm bells should be ringing with the early signs of a 'back to business' attitude in the City and little evidence that policymakers are taking measures to ensure the next economic recovery is better balanced than the last one," said Tony Dolphin, senior economist at the IPPR.
The report warned that unless urgent action was taken, the banking crisis might not be the last of its type.
On Monday, President Obama issued a warning to banks that were ignoring the lessons of the financial crisis.
"We will not go back to the days of reckless behaviour and unchecked excess at the heart of this crisis," he said.
He called on Wall Street to support "the most ambitious overhaul of the financial system since the Great Depression". It has so far met with opposition in the banking industry.
Speaking on the BBC World News channel, John Lipsky, deputy managing director of the International Monetary Fund, defended the international response to the crisis, saying "some fundamental changes" had already been made or were underway.
BBC AFTERSHOCK SEASON
The BBC reports on the first anniversary of the credit crunch across radio, TV, and online.
"We have made important changes in creating crisis prevention instruments that have a chance of success in a world of cross-border finance," he said.
"In addition, the international community has come together to provide substantial new resources for the fund."
As for the financial industry itself, Bob Diamond, the chief executive of Barclays Capital, told the BBC he thought lessons had been learnt.
"We've made mistakes. The important thing is to learn from those mistakes and change the way we do things," said Mr Diamond, whose bank bought Lehman Brothers' US operations out of bankruptcy.
"In future, banks will be operating with more equity, with less leverage, with bigger buffers of liquidity."
The IMF's Mr Lipsky, however, said there was still some way to go.
"It remains to be seen if the global community can carry through all the changes [to regulation and supervision] that are recognised as necessary, but will need political determination to succeed."
UK Prime Minister Gordon Brown said he was determined that world leaders meeting in Pittsburgh next week would "complete the unfinished business" of cleaning up banks - including establishing rules on bonuses.
The Group of 20 (G20) richest nations will meet to discuss the state of the global economy.
Bankers' bonuses - which have been blamed for encouraging risk-taking and prompting the acts that caused the financial crisis - are expected to be one of the most prominent issues.
The G20 has agreed that bonuses should be deferred in order to reward long-term success rather than short-term risk-taking, but have so far opposed mandatory caps on banker compensation.
"At the G20 meeting, the big concept seems to be executive salaries," said Professor Robert Shiller from Yale University. "That's a politically popular movement. But it's not central to making the system work better.
"There's a lot of boring stuff that has to be done," he added.
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