Exhibit 5.1 TROUTMAN SANDERS LLP ATTORNEYS AT LAW A LIMITED LIABILITY PARTNERSHIP TROUTMAN SANDERS LLP ATTORNEYS AT LAW A LIMITED LIABILITY PARTNERSHIP BANK OF AMERICA PLAZA 600 PEACHTREE STREET, N.E. - SUITE 5200 ATLANTA, GEORGIA 30308-2216 www.troutmansanders.com TELEPHONE: 404-885-3000 June 30, 2005 Mississippi Power Company 2992 West Beach Gulfport, Mississippi 39501 Re: Registration Statement on Form S-3 Ladies and Gentlemen: We have acted as counsel to Mississippi Power Company (the "Company") in connection with the Registration Statement, on Form S-3 (Registration Statement Nos. 333-108156, 333-108156-01 and 333-108156-02) (the "Registration Statement"), relating to $30,000,000 aggregate principal amount of the Company's Series G 5.40% Senior Notes due July 1, 2035 (the "Notes"). The Notes will be issued pursuant to the Senior Note Indenture dated as of May 1, 1998 between the Company and Deutsche Bank Trust Company Americas (formerly known as Bankers Trust Company), as trustee (the "Trustee"), as heretofore supplemented and amended and as further supplemented and amended by a Seventh Supplemental Indenture dated as of June 30, 2005 (collectively, the "Indenture"). We have examined the Registration Statement and the Indenture, which has been filed with the Securities and Exchange Commission (the "Commission") as an exhibit to the Registration Statement. We have also examined the originals, or duplicates or certified or conformed copies, of such records, agreements, instruments and other documents and have made such other and further investigations as we have deemed relevant and necessary in connection with the opinions expressed herein. As to questions of fact material to this opinion, we have relied upon certificates of public officials and of officers and representatives of the Company. In rendering the opinions set forth below, we have assumed the genuineness of all signatures, the legal capacity of natural persons, the authenticity of all documents submitted to us as originals, the conformity to original documents of all documents submitted to us as duplicates or certified or conformed copies and the authenticity of the originals of such latter documents. We have also assumed that the Indenture is the valid and legally binding obligation of the Trustee. Based upon the foregoing, and subject to the qualifications and limitations stated herein, we are of the opinion that the Notes are valid, binding and legal obligations of the Company enforceable against the Company in ATLANTA o HONG KONG o LONDON o NEW YORK o NORFOLK o RALEIGH o RICHMOND o TYSONS CORNER o VIRGINIA BEACH o WASHINGTON, D.C. Mississippi Power Company June 30, 2005 Page 2 accordance with their terms (subject to applicable bankruptcy, insolvency, reorganization, moratorium and other similar laws relating to or affecting creditors' rights generally and to general principles of equity, whether considered in a proceeding at law or in equity). In rendering the foregoing opinion, with respect to matters of New York law, we have relied on the opinion of Dewey Ballantine LLP attached hereto as Annex I. We are members of the State Bar of Georgia and we do not express any opinion herein concerning any law other than the law of the State of Georgia and the federal law of the United States and, to the extent set forth herein, the law of the State of New York. We hereby consent to the filing of this opinion with the Commission as an exhibit to the Registration Statement and to the statements with respect to our name under the heading "Legal Matters" in the prospectus forming part of the Registration Statement. In giving the foregoing consent, we do not hereby admit that we come within the category of persons whose consent is required under Section 7 of the Securities Act of 1933, as amended, or the rules and regulations of the Commission thereunder. This opinion may not be furnished or quoted to, or relied upon by, any other person for any purpose, without our prior written consent. Very truly yours, /s/ TROUTMAN SANDERS LLP TROUTMAN SANDERS LLP June 30, 2005 Troutman Sanders LLP 600 Peachtree Street, N.E. Suite 5200 Atlanta, Georgia 30308 RE: Registration Statement on Form S-3 Ladies and Gentlemen: We have acted as counsel to the underwriter in connection with the Registration Statement on Form S-3 (Registration Statement Nos. 333-108156, 333-108156-01 and 333-108156-02 ) (the "Registration Statement"), relating to $30,000,000 aggregate principal amount of Series G 5.40% Senior Notes due July 1, 2035 (the "Notes") of Mississippi Power Company (the "Company"). The Notes will be issued pursuant to the Senior Note Indenture dated as of May 1, 1998 between the Company and Deutsche Bank Trust Company Americas (formerly known as Bankers Trust Company), as trustee (the "Trustee"), as heretofore supplemented and amended and as further supplemented and amended by a Seventh Supplemental Indenture dated as of June 30, 2005 (collectively, the "Indenture"). We have examined the Registration Statement and the Indenture, which has been filed with the Securities and Exchange Commission as an exhibit to the Registration Statement. We have also examined the originals, or duplicates or certified or conformed copies, of such records, agreements, instruments and other documents and have made such other and further investigations as we have deemed relevant and necessary in connection with the opinions expressed herein. As to questions of fact material to this opinion, we have relied upon certificates of public officials and of officers and representatives of the Company. In rendering the opinions set forth below, we have assumed the genuineness of all signatures, the legal capacity of natural persons, the authenticity of all documents submitted to us as originals, the conformity to original documents of all documents submitted to us as duplicates or certified or conformed copies and the authenticity of the originals of such latter documents. We have also assumed that the Indenture is the valid and legally binding obligation of the Trustee. June 30, 2005 Page 2 Based upon the foregoing, and subject to the qualifications and limitations stated herein, we are of the opinion that the Notes are valid, binding and legal obligations of the Company enforceable against the Company in accordance with their terms (subject to applicable bankruptcy, insolvency, reorganization, moratorium and other similar laws relating to or affecting creditors' rights generally and to general principles of equity, whether considered in a proceeding at law or in equity). We are members of the State Bar of New York and we do not express any opinion concerning any law other than the law of the State of New York. This opinion is furnished solely for your benefit in connection with your rendering an opinion to the Company to be filed as Exhibit 5.1 to the Registration Statement and we hereby consent to your attaching this opinion as an annex to such opinion. This opinion may not be relied upon by you for any other purpose, or quoted to or relied upon by any other person, firm or entity for any purpose, without our prior written consent. In giving our consent to your attaching this opinion to the opinion being rendered by you, we do not thereby admit that we come within the category of persons whose consent is required under Section 7 of the Securities Act of 1933, as amended, or the rules and regulations of the Securities and Exchange Commission thereunder. Very truly yours, /s/ DEWEY BALLANTINE LLP DEWEY BALLANTINE LLP