On a 12-month comparison, the unemployment rate rose by 1.6 percentage points, Istat said in a statement.
The number of people looking for work rose to 3.194 million - a 0.9 percent increase from August and 14 percent higher than in September 2012.
Among the active working population of 15-24-year-olds, the unemployment rate also hit a new record of 40.4 percent, up 0.2 percent on August and 4.4 points higher than a year ago, Istat said.
Over one young person in 10 (10.9 percent) in that age range is looking for work, it said.
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Italy has been mired in a recession for two years and unemployment has been rising for months. The government has said it is expecting a gradual recovery to start towards the end of this year.