The cut marked the second half-point reduction in the funds rate this month. The Fed slashed the rate by that amount in a coordinated move with foreign central banks on Oct. 8.
In a brief statement explaining Wednesday's action, the Fed said the "intensification of financial market turmoil is likely to exert additional restraint on spending, partly by further reducing the ability of households and business to obtain credit."
The central bank said it had room to lower rates because the spreading economic weakness was lowering the risks that inflation would get out of control. Indeed, the weakness has caused dramatic declines in the price of oil and other commodities.
While many economists believe the country has already fallen into a recession, they think the aggressive efforts by the Fed to cut rates and take other actions to unfreeze credit markets will keep the country from plunging into a prolonged and deep downturn.
The Fed's action was expected to be quickly followed by a reduction by commercial banks in their prime lending rate, the benchmark for millions of consumer and business loans, by a similar half-point.