SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 6-K

Report of Foreign Private Issuer
Pursuant to Rule 13a-16 or 15d-16 of the

Securities Exchange Act of 1934

For the month of April 2014

Commission File Number 1-13758

PORTUGAL TELECOM, SGPS, S.A.

(Exact name of registrant as specified in its charter)

Av. Fontes Pereira de Melo, 40
1069 - 300 Lisboa, Portugal

(Address of principal executive office)

Indicate by check mark whether the registrant files or will file annual reports under cover Form 20-F or Form 40-F.

Form 20-F x  Form 40-F o

Indicate by check mark whether the registrant by furnishing the information contained in this Form is also thereby furnishing the information to the Commission pursuant to Rule 12g3-2(b) under the Securities Exchange Act of 1934.

Yes o  No x

Announcement  |  Lisbon  |  3 April 2014

Material Fact disclosed by Oi

Portugal Telecom, SGPS S.A. (“PT”) hereby informs on the material fact disclosed by Oi, S.A. (“Oi”) on the revocation of the suspension of the public offering, according to the company’s announcement attached hereto.

www.telecom.pt

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OI S.A.

Corporate Taxpayers’ Registry

(CNPJ/MF) No. 76.535.764/0001-43

Board of Trade (NIRE) 33.30029520-8

Publicly-Held Company

MATERIAL FACT

Revocation of Suspension of Public Offering

Oi S.A. (“Oi” or the “Company”, BM&FBOVESPA: OIBR3, OIBR4; NYSE: OIBR and OIBR.C), in compliance with article 157, paragraph 4 of Law No. 6,404/76 and CVM Instruction No. 358/02 and, in addition to the Material Fact dated as of March 27, 2014, notifies its shareholders and the market in general that as of the date hereof, Oi received the Official Letter No. 153/2014 from the Brazilian Securities Commission (Comissão de Valores Mobiliários — CVM) (“CVM”), whereby the CVM informed Oi of the revocation of the suspension of Oi’s public offering, whose request for registration is under review by the CVM (the “Offering”).

Given the CVM’s decision to revoke the suspension, the Company discloses that it will resume the Offering and will maintain the market promptly informed.

Rio de Janeiro, April 1, 2014.

OI S.A.

Bayard De Paoli Gontijo

Chief Financial Officer and Investor Relations Officer

Additional Information and Where to Find It:

Oi S.A. (“Oi”) has filed a registration statement (including a prospectus) with the U.S. Securities and Exchange Commission (the “SEC”) for the offering to which this communication relates. Before you invest, you should read the prospectus in that registration statement and other documents Oi has filed with the SEC for more complete information about Oi and this offering. You may get these documents for free by visiting EDGAR on

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the SEC’s website at www.sec.gov. Alternatively, Oi will arrange to send you the prospectus after filing if you request it by calling toll-free 1-855-672-2332.

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SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

Date: April 3, 2014

FORWARD-LOOKING STATEMENTS

This document may contain forward-looking statements. These statements are statements that are not historical facts, and are based on management’s current view and estimates of future economic circumstances, industry conditions, company performance and financial results. The words “anticipates”, “believes”, “estimates”, “expects”, “plans” and similar expressions, as they relate to the company, are intended to identify forward-looking statements. Statements regarding the declaration or payment of dividends, the implementation of principal operating and financing strategies and capital expenditure plans, the direction of future operations and the factors or trends affecting financial condition, liquidity or results of operations are examples of forward-looking statements. Such statements reflect the current views of management and are subject to a number of risks and uncertainties. There is no guarantee that the expected events, trends or results will actually occur. The statements are based on many assumptions and factors, including general economic and market conditions, industry conditions, and operating factors. Any changes in such assumptions or factors could cause actual results to differ materially from current expectations.

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