Company: SOJE
Filing Date: 2025-02-25
Form Type: 424B5
Source: 0000092122-25-000022
Chunk: 0

Company: SOUTHERN CO
Filing Date: 2025-02-25
Form: 424B5
Chunk 0
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Filed Pursuant to Rule 424(b)(5)

Registration No. 333-277138

This Preliminary Prospectus Supplement and the accompanying Prospectus relate to an effective registration statement under the Securities Act of 1933, as amended, but the Preliminary Prospectus Supplement is not complete and may be changed. This Preliminary Prospectus Supplement and the accompanying Prospectus are not an offer to sell these securities and are not soliciting an offer to buy these securities in any jurisdiction where the offer or sale is not permitted.

### SUBJECT TO COMPLETION
<div align='center'>PRELIMINARY PROSPECTUS SUPPLEMENT DATED FEBRUARY 25, 2025</div>

PROSPECTUS SUPPLEMENT

(To Prospectus dated February 16, 2024)

<div align='center'>$</div>

#### .

<div align='center'>Series 2025B % Fixed-to-Fixed Reset Rate
Junior Subordinated Notes due March 15, 2055</div>

The Series 2025B % Fixed-to-Fixed Reset Rate Junior Subordinated Notes due March 15, 2055 (the “Series 2025B Junior Subordinated Notes”) will bear interest (i) from and including the date of original issuance to, but excluding, March 15, 2035 at an annual rate of % and (ii) from and including March 15, 2035 during each Interest Reset Period (as defined herein) at an annual rate equal to the Five-Year Treasury Rate (as defined herein) as of the most recent Reset Interest Determination Date (as defined herein), plus %; provided, that the interest rate during any Interest Reset Period will not reset below % (which equals the initial interest rate on the Series 2025B Junior Subordinated Notes). Interest will be payable semi-annually in arrears on March 15 and September 15 of each year, beginning on September 15, 2025. The Series 2025B Junior Subordinated Notes will be issued in registered form and in denominations of $2,000 and integral multiples of $1,000 in excess thereof. The Series 2025B Junior Subordinated Notes will mature on March 15, 2055.

So long as no Event of Default (as defined herein) has occurred and is continuing, The Southern Company may defer interest payments on the Series 2025B Junior Subordinated Notes on one or more occasions for up to 10 consecutive years as described in