<TABLE> <S> <C>

<PAGE>
 
<ARTICLE> 9
<LEGEND>
THIS SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATION EXTRACTED FROM THE
CONSOLIDATED STATEMENT OF CONDITION, THE CONSOLIDATED STATEMENT OF EARNINGS, THE
CONSOLIDATED STATEMENT OF CASH FLOWS OF ITEM 1 OF PART 1 AND TABLES 2, 6 AND 7
OF ITEM 2 OF PART 1 OF THE AMSOUTH BANCORPORATION FORM 10-Q FOR THE QUARTERLY
PERIOD ENDED SEPTEMBER 30, 1998 AND IS QUALIFIED IN ITS ENTIRETY BY REFERENCE TO
SUCH FINANCIAL STATEMENTS.
</LEGEND>
<MULTIPLIER> 1,000
       
<S>                             <C>
<PERIOD-TYPE>                   9-MOS
<FISCAL-YEAR-END>                          DEC-31-1998
<PERIOD-START>                             JAN-01-1998
<PERIOD-END>                               SEP-30-1998
<CASH>                                         532,758
<INT-BEARING-DEPOSITS>                               0
<FED-FUNDS-SOLD>                                   500
<TRADING-ASSETS>                                 2,689
<INVESTMENTS-HELD-FOR-SALE>                  3,281,129
<INVESTMENTS-CARRYING>                       2,297,091
<INVESTMENTS-MARKET>                         2,328,440
<LOANS>                                     12,527,168
<ALLOWANCE>                                    175,046
<TOTAL-ASSETS>                              19,693,343
<DEPOSITS>                                  13,017,167
<SHORT-TERM>                                 1,595,181
<LIABILITIES-OTHER>                            388,117
<LONG-TERM>                                  3,254,921
<PREFERRED-MANDATORY>                                0
<PREFERRED>                                          0
<COMMON>                                       135,090
<OTHER-SE>                                   1,302,867
<TOTAL-LIABILITIES-AND-EQUITY>              19,693,343
<INTEREST-LOAN>                                810,610
<INTEREST-INVEST>                              282,113
<INTEREST-OTHER>                                 4,461
<INTEREST-TOTAL>                             1,096,634
<INTEREST-DEPOSIT>                             377,399
<INTEREST-EXPENSE>                             576,831
<INTEREST-INCOME-NET>                          519,803
<LOAN-LOSSES>                                   45,834
<SECURITIES-GAINS>                               5,218
<EXPENSE-OTHER>                                434,444
<INCOME-PRETAX>                                300,899
<INCOME-PRE-EXTRAORDINARY>                     300,899
<EXTRAORDINARY>                                      0
<CHANGES>                                            0
<NET-INCOME>                                   194,337
<EPS-PRIMARY>                                     1.62
<EPS-DILUTED>                                     1.60
<YIELD-ACTUAL>                                    3.91
<LOANS-NON>                                     74,141
<LOANS-PAST>                                    29,586
<LOANS-TROUBLED>                                     0
<LOANS-PROBLEM>                                      0
<ALLOWANCE-OPEN>                               179,197
<CHARGE-OFFS>                                   52,712
<RECOVERIES>                                    17,627
<ALLOWANCE-CLOSE>                              175,046
<ALLOWANCE-DOMESTIC>                                 0
<ALLOWANCE-FOREIGN>                                  0
<ALLOWANCE-UNALLOCATED>                              0
        

</TABLE>