Company: SOJE
Filing Date: 2025-01-08
Form Type: 424B5
Source: 0000092122-25-000002
Chunk: 2

Company: SOUTHERN CO
Filing Date: 2025-01-08
Form: 424B5
Chunk 2
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 expenses, to The Southern Company will be $ , $ and $ , respectively.

The Series 2025A Junior Subordinated Notes are expected to be delivered on or about January , 2025 through the book-entry facilities of The Depository Trust Company for the accounts of its participants, including Euroclear Bank SA/NV (“Euroclear”), as operator of the Euroclear system, or Clearstream Banking, S.A., Luxembourg (“Clearstream”).

<div align='center'>Joint Book-Running Managers</div>

| BofA Securities |     | J.P. Morgan |     | Morgan Stanley |     | RBC Capital Markets |     | Wells Fargo Securities |

January , 2025

No dealer, salesperson or other person is authorized to give any information or to represent anything not contained in this Prospectus Supplement, the accompanying Prospectus or any written communication from The Southern Company or the underwriters specifying the final terms of the offering. Neither The Southern Company nor any underwriter takes any responsibility for, nor can it provide any assurance as to the reliability of, any other information that others may give you. This Prospectus Supplement, the accompanying Prospectus and any written communication from The Southern Company or the underwriters specifying the final terms of the offering is an offer to sell only the Series 2025A Junior Subordinated Notes offered hereby, and only under circumstances and in jurisdictions where it is lawful to do so. The information incorporated by reference or contained in this Prospectus Supplement, the accompanying Prospectus and any written communication from The Southern Company or the underwriters specifying the final terms of the offering is current only as of its respective date.

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

### TABLE OF CONTENTS
|                                                                          |     | Page |
| Prospectus Supplement                                                    |     |      |
| Summary                                                                  |     |  S-3 |
| Risk Factors                                                             |     |  S-7 |
| Available Information                                                    |     |  S-8 |
| Incorporation of Certain Documents by Reference                          |     |  S-8 |
| Selected Financial Information                                           |     |  S-9 |
| Use of Proceeds                                                          |     | S-10 |
| Description of the Series 2025A Junior Subordinated Notes                |     | S-10 |
| Material United States Federal Income Tax Considerations                 |     | S-15 |
| Underwriting (Conflicts of Interest)                                     |     | S-21 |
| Legal Matters                                                            |     | S-26 |
| Prospectus