That was weaker than the 0.3 percent rate of decline first estimated a month ago, and marked the worst showing since the economy contracted at a 1.4 percent pace in the third quarter of 2001, when the nation was suffering through its last recession.
GDP measures the value of all goods and services produced within the U.S. and is considered the best barometer of the country's economic fitness.
The new reading on GDP underscores just how quickly the economy deteriorated as housing, credit and financial crises intensified. The economy logged growth of 2.8 percent in the second quarter.
The new, lower third-quarter reading matched economists' forecasts. The downgrade from the initial estimate mostly reflected an even sharper cut back in spending by consumers and less brisk sales growth of U.S. exports.
American consumers - the lifeblood of the economy - slashed spending in the third quarter at a 3.7 percent pace. That was deeper than the 3.1 percent cut initially reported and marked the biggest reduction since the second quarter of 1980, when the country was in the grip of recession.
Consumers are hunkering down amid job losses, tanking investment portfolios and sinking home values, which are making them nervous about spending.
Underscoring the strain faced by consumers, the report showed that Americans' disposable income fell at an annual rate of 9.2 percent in the third quarter, the largest quarterly drop on records dating back to 1947. The government's initial estimate had showed a record 8.7 percent decline in disposable income for the quarter.
Sales of U.S. exports grew at a 3.4 percent pace in the third quarter. That was lower than a 5.9 percent growth rate intially estimated and marked a sharp slowdown from the second quarter's blistering 12.3 percent growth rate. The deceleration reflects less demand from overseas buyers coping with their own economic problems.
Home builders slashed spending at a 17.6 percent pace, marking the 11th straight quarterly cut and fresh evidence of the depth of the housing slump.
To help revive the economy, the Federal Reserve is expected to lower interest rates when its meets on Dec. 16, its last session of the year. Last month, the Fed dropped its key rate to 1 percent, a level seen only once before in the last half-century.
So far, though, the Fed's rate reductions, a $700 billion financial bailout package and a flurry of other radical actions have been unable to break though a dangerous credit clog, restore stability to financial markets and help the sinking economy.
Banks are failing and storied Wall Street firms have been crippled by the crises. Home foreclosures have soared and jobs are vanishing.
President-elect Barack Obama sees as a top priority getting Congress to enact a massive economic stimulus package that he says will generate millions of new jobs.
The nation's unemployment rate is at 6.5 percent, a 14-year high, and will climb higher. Employers have cut payrolls every month so far this year and more losses are expected in the months ahead.
Given all the stresses, consumers are expected to burrow further, making it likely the economy will continue to shrink through the rest of this year and into 2009, more than fulfilling a classic definition of a recession. That is, two straight quarters of contracting GDP.