UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13D/A

(Rule 13d-101)

(Information to be Included in Statements Filed Pursuant to

§ 240.13d-1(a) and Amendments Thereto Filed

Pursuant to § 240.13d-2(a))

Under the Securities Exchange Act of 1934

(Name of Issuer)

(Title of Class of Securities)

(CUSIP Number)

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

(Date of Event Which Requires Filing of This Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§ 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box.  ¨

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SCHEDULE 13D

This Amendment No. 5 (this “Amendment”) amends and supplements the statement on Schedule 13D (the “Schedule 13D”) dated October 24, 2008, as subsequently amended by Amendment No. 1 dated September 17, 2009, Amendment No. 2 dated October 27, 2009, and Amendment No. 3 dated February 8, 2011, Amendment No. 4 dated September 7, 2011, filed jointly by Telefónica, S.A., a corporation organized under the laws of the Kingdom of Spain (“Telefónica”), and Telefónica Internacional, S.A.U., a wholly-owned subsidiary of Telefónica (“Telefónica Internacional”), with respect to the ordinary shares, HK$0.10 par value per share, of China Unicom (Hong Kong) Limited, a telecommunications company organized under the laws of Hong Kong (“China Unicom”). Capitalized terms used in this Amendment without definition have the meanings ascribed to them in the Schedule 13D.

Introduction

On June 10, 2012, Telefónica, S.A. through its 100% subsidiary, Telefónica Internacional, S.A.U. (hereinafter “Telefonica”), and China United Network Communications Group Company Limited (“Unicom Parent”) through a 100% owned subsidiary, have signed a definitive agreement under which the latter will acquire 1,073,777,121 shares of China Unicom (Hong Kong) Limited (“China Unicom”), owned by Telefonica (equivalent to 4.56% of the share capital of China Unicom), at a price of HK$10.21 per share, for a total amount of HK$10,963.3 million, approximately € 1,128.9 million at current exchange rates.

The acquisition of the shares is subject to the relevant regulatory authorizations and is expected to be completed by no later than July 31, 2012.

Item 4, 5 and 7 of the Schedule 13D are hereby amended and supplemented to add the following:

Item 4. Purpose of the transaction.

While the transaction reflects Telefonica, S.A. Board of Directors decision to proactively manage its asset portfolio, both Telefónica, S.A. and China Unicom continue to be fully committed to their Strategic Alliance with a fruitful strategic cooperation between the two parties on different areas such as MNCs, international business, procurement, roaming and technology among others, while exploring new opportunities to work together in the digital world.

This transaction will allow Telefónica, S.A. to increase its financial flexibility, while at the same time it will continue to be a key shareholder of China Unicom, with a 5.01% stake.

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Item 5. Interest in Securities of the Issuer.

As a consequence of the consummation of the aforementioned agreement, Telefónica Internacional currently is the beneficial owner of 1,180,601,587 ordinary shares of China Unicom, representing 5. 01% of its ordinary share capital. Telefónica, as the parent company of Telefónica Internacional, has shared power to vote or to direct the vote, and the shared power to dispose or to direct the disposition of, such ordinary shares of China Unicom.

Item 7 Material to be Filed as Exhibits

Exhibit 4:

Agreement, dated June 10, 20012 between Telefónica Internacional, S.A.U., and a 100% owned subsidiary of China United Network Communications Group Company Limited.

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SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Dated: June 13, 2012

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Exhibit Index

Exhibit No.

Schedule I

Executive Officers and Directors of Telefónica

The directors and executive officers of Telefónica as of the date hereof are set forth below. The business address of each director or executive officer is that of Telefónica located at Distrito C, Ronda de la Comunicación s/n, 28050 Madrid, Spain. Unless noted otherwise, each of the named individuals is a citizen of the Kingdom of Spain.

Directors and Officers of Telefónica

MEMBERS OF THE BOARD OF DIRECTORS

MEMBERS OF THE BOARD OF DIRECTORS

Executive Officers

Exhibit 4

Execution version

TELEFÓNICA INTERNACIONAL, S.A.U.

AND

CHINA NETCOM GROUP CORPORATION (BVI) LIMITED

SHARE PURCHASE AGREEMENT

FOR THE SALE AND PURCHASE OF SHARES IN

CHINA UNICOM (HONG KONG) LIMITED

CONTENTS

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THIS AGREEMENT is made on 10 June 2012

BETWEEN:

RECITALS:

THE PARTIES AGREE as follows:

In this Agreement:

“Affiliate” means, in relation to a person, any other person which, directly or indirectly, controls, is controlled by or is under the common control of the first mentioned person, where “control” means the ownership, directly or indirectly, of more than 50 per cent. of the voting shares, registered capital or other equity interest of the relevant person or the possession, directly or indirectly, of the power to direct the shareholders’ general meeting, to appoint or elect a majority of the directors, or otherwise to direct the management of the relevant person;

“Applicable Laws” means with respect to any person, any laws, rules, regulations, guidelines, directives, treaties, judgments, determination, orders or notices of any Authority or stock exchange that is applicable to such person including, for the avoidance of doubt, the Listing Rules and the Takeovers Code;

“Authority” means any national, provincial, municipal or local government, administrative or regulatory body or department, court, tribunal, arbitrator or any body that exercises the function of a regulator;

“Business Day” means a day other than a Saturday or Sunday or public holiday in Hong Kong, the PRC or Spain;

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“Buyer Warranty” means a statement contained in Schedule 3 and “Buyer Warranties” means all those statements;

“Company” means China Unicom (Hong Kong) Limited, a company incorporated in Hong Kong whose registered office is at 75th Floor, The Centre, 99 Queen’s Road Central, Hong Kong and whose shares are listed in the main board of The Stock Exchange of Hong Kong Limited (Stock Code: 0762);

“Completion” means completion of the transfer of the Sale Shares in accordance with this Agreement;

“Completion Date” means the date which is 10 Business Days after the date (not being later than the Longstop Date) on which the Condition is satisfied, or such other date as the Seller and the Buyer may agree in writing;

“Condition” means the condition set out in Clause 3.1;

“Confidential Information” means all information which relates to the provisions or subject matter of this Agreement or any documents referred to in this Agreement or the negotiations relating to this Agreement;

“Encumbrance” means a mortgage, pledge, lien, option, restriction, right of first refusal, right of pre-emption, third-party right or interest, other encumbrance or security interest of any kind, or another type of preferential arrangement (including, without limitation, a title transfer or retention arrangement) having similar effect;

“HK$” means Hong Kong dollars, the lawful currency of Hong Kong;

“HKIAC” has the meaning specified in Clause 13.2;

“Hong Kong” means the Hong Kong Special Administrative Region of the People’s Republic of China;

“Listing Rules” means the Rules Governing the Listing of Securities on The Stock Exchange of Hong Kong Limited;

“Lock-up Period” has the meaning specified in Clause 6.1;

“Longstop Date” means 31 July 2012 (or such other date as the Seller and the Buyer may agree in writing);

“Notice” has the meaning specified in Clause 12.1;

“NDRC” means the National Development and Reform Commission (or its provincial or local counterpart) of the PRC;

“PRC” or “Mainland” means the People’s Republic of China excluding, for the purposes of this Agreement, Hong Kong, Macau and Taiwan;

“Purchase Price” has the meaning specified in Clause 2.2;

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“Relevant Shares” has the meaning specified in Clause 6.1;

“Sale Shares” has the meaning specified in Recital (A);

“SASAC” means the State-owned Assets Supervision and Administration Commission of the State Council of the PRC (or its provincial or local counterpart);

“Seller Warranty” means a statement contained in Schedule 2 and “Seller Warranties” means all those statements;

“Seller’s Bank Account” means the Seller’s bank account, details of which shall be notified by the Seller to the Buyer at least 3 Business Days before the Completion Date;

“SFO” means the Securities and Futures Ordinance (Cap. 571 of the Laws of Hong Kong);

“Shares” means ordinary shares of HK$0.10 each in the issued share capital of the Company;

“Takeovers Code” means The Codes on Takeovers and Mergers and Share Repurchases published by the Securities and Futures Commission of Hong Kong; and

“Tax” means any form of taxation, levy, duty, charge, contribution, or withholding of whatever nature (including any related fine, penalty, surcharge or interest) imposed, collected or assessed by, or payable to, any national, provincial, municipal or local government or other authority, body or official anywhere in the world exercising a fiscal, revenue, customs or excise function.

In this Agreement, a reference to:

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The headings in this Agreement do not affect its interpretation.

The Seller agrees to sell, and the Buyer agrees to buy, the Sale Shares with effect from Completion with all rights then attaching to them and free of any Encumbrance.

The purchase price of each Sale Share is HK$10.21, with the aggregate purchase price for the Sale Shares being HK$10,963,264,405.41 (the “Purchase Price”). The Purchase Price (less the amounts agreed to be deducted pursuant to Clause 10.2) shall be payable by the Buyer to the Seller on Completion.

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For the avoidance of doubt, if Completion does not take place on the Completion Date because both parties fail to comply with any of their respective obligations under this Clause 4 and Schedule 1 (whether such failure by the party or parties amounts to a material breach or not), the parties shall consult with each other in good faith with a view to postponing Completion to a date falling no later than 5 Business Days thereafter or terminating this Agreement, the decision in respect of which shall be in each party’s absolute discretion.

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Subject to Clause 8.2, each party undertakes to the other party that it shall:

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Notwithstanding Clause 9.2, the Seller, the Buyer or any of their respective Affiliates may, before or after Completion, make or send a public announcement, communication or circular concerning the transactions referred to in this Agreement provided that it has first obtained the other party’s consent, which may not be unreasonably withheld or delayed.

Clause 9.1 does not apply to a public announcement, communication or circular required by Applicable Laws, by a rule of a listing authority or stock exchange on which the shares of the Company or a party (or its ultimate holding company) are listed or traded, or by an Authority with relevant powers to which either party is subject or submits, whether or not the requirement has the force of law, provided that the public announcement, communication or circular shall so far as is practicable be made after consultation with the other party and after taking into account the reasonable requirements of the other party as to its timing, content and manner of making or despatch.

Except where this Agreement or the relevant document provides otherwise, each party shall pay its own costs relating to the negotiation, preparation, execution and performance by it of this Agreement and of each document referred to in it.

All stamp duty and any trading fees or transaction levies payable in connection with the transfer of the Sale Shares shall be paid and borne in equal shares by the Seller on the one hand and the Buyer on the other hand.

Subject to Clause 10.2, each of the parties shall be responsible for its own Tax liabilities arising from the transfer of the Sale Shares under this Agreement.

An amendment of this Agreement is valid only if it is in writing and signed by or on behalf of each party.

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The failure to exercise or delay in exercising a right or remedy provided by this Agreement or by law does not impair or constitute a waiver of the right or remedy or an impairment of or a waiver of other rights or remedies. No single or partial exercise of a right or remedy provided by this Agreement or by law prevents further exercise of the right or remedy or the exercise of another right or remedy.

Each party’s rights and remedies contained in this Agreement are cumulative and not exclusive of rights or remedies provided by law.

Except to the extent that they have been performed and except where this Agreement provides otherwise, the obligations contained in this Agreement remain in force after Completion.

The invalidity, illegality or unenforceability of a provision of this Agreement does not affect or impair the validity of the remainder of this Agreement.

This Agreement may be executed in any number of counterparts, each of which when executed and delivered is an original and all of which together evidence the same agreement.

Each of the parties agrees to perform (or procure the performance of) all such acts and things and/or to execute and deliver (or procure the execution and delivery of) all such documents, as may be required by law or as may be necessary or reasonably requested by another party for giving full effect to this Agreement. Unless otherwise agreed, each party shall be responsible for its own costs and expenses incurred in connection with the provisions of this Clause 11.7.

This Agreement constitutes the entire agreement and supersedes any previous agreement between the parties relating to the subject matter of this Agreement.

No party may assign or in any other way alienate any of its rights under this Agreement whether in whole or in part.

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A notice or other communication under or in connection with this Agreement (a “Notice”) shall be:

Unless there is evidence that it was received earlier, a Notice is deemed given if:

The address and fax number referred to in Clause 12.1.3 is:

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This Agreement is governed by the laws of Hong Kong.

Any dispute, controversy or claim arising out of or relating to this Agreement, or the breach, termination or invalidity thereof, shall be settled by arbitration in Hong Kong at the Hong Kong International Arbitration Centre (“HKIAC”) under the Hong Kong International Arbitration Centre Administered Arbitration Rules in force when the Notice of Arbitration is submitted in accordance with these Rules.

The arbitration tribunal shall comprise of three arbitrators.

The arbitration proceedings shall be conducted in English.

Nothing in this Clause 13 shall be construed as preventing any party from seeking interim relief in any court of competent jurisdiction.

The arbitration award shall be final and binding on the parties from the day it is made and the parties agree to be bound thereby and to act accordingly.

Judgement upon any award rendered by the arbitration tribunal may be entered, and application for judicial confirmation or recognition or enforcement of the award may be made by or in any court of competent jurisdiction, and each of the parties hereto irrevocably submits to the jurisdiction of such court for confirmation or recognition or enforcement of any award rendered by the arbitral tribunal in accordance with, inter alia, the United Nations Convention on the Recognition and Enforcement of Foreign Arbitral Awards and the Arrangement Concerning Mutual Enforcement of Arbitration Awards between the Mainland and the Hong Kong Special Administrative Region.

During the conduct of any arbitration proceedings pursuant to this Clause 13, this Agreement shall remain in full force and effect in all respects except for the matter under arbitration and the parties shall continue to perform their obligations hereunder, except for those obligations involved in the matter under dispute, and to exercise their rights hereunder.

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This Agreement is written in English. If this Agreement is translated into another language, the English language text prevails.

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SCHEDULE 1

COMPLETION REQUIREMENTS

At Completion the Seller shall deliver to the Buyer:

in each case certified to be true by a director or secretary of the Seller or its legal advisers.

At Completion the Buyer shall deliver to the Seller:

in each case certified to be true by a director or secretary of the Buyer or its legal advisers; and

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SCHEDULE 2

SELLER WARRANTIES

The Seller is a corporation duly incorporated under the laws of Spain and has been in continuous existence since incorporation.

The Seller has the right, power and authority, and has taken all action necessary to execute, deliver, exercise its rights and perform its respective obligations, under this Agreement and each document to be executed at or before Completion, and to carry out the transactions contemplated hereby and thereby.

As at Completion, the Seller has obtained all necessary consents, approvals and authorisations from the Authorities and any other entities in relation to the transaction contemplated under this Agreement (if applicable) and no other consents, approvals or other authorisations is required from any Authority under the Applicable Laws in relation to such transaction.

The obligations of the Seller under this Agreement and each document to be executed at or before Completion constitutes, or when the relevant document is executed will constitute, valid, legal and binding obligations and are enforceable in accordance with their terms.

There is no Encumbrance, and there is no agreement, arrangement or obligation to create or give an Encumbrance, in relation to any of the Sale Shares. No person has claimed to be entitled to an Encumbrance in relation to any of the Sale Shares.

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SCHEDULE 3

BUYER WARRANTIES

The Buyer is a limited liability company duly incorporated under the laws of the British Virgin Islands and has been in continuous existence since incorporation.

The Buyer has the right, power and authority, and has taken all action necessary to execute, deliver, exercise its rights and perform its respective obligations, under this Agreement and each document to be executed at or before Completion, and to carry out the transactions contemplated hereby and thereby.

As at Completion, the Buyer has obtained all necessary consents, approvals and authorisations from the Authorities and any other entities in relation to the transaction contemplated under this Agreement (if applicable) and no other consents, approvals or other authorisations is required from any Authority under the Applicable Laws in relation to such transaction.

The obligations of the Buyer under this Agreement and each document to be executed at or before Completion constitutes, or when the relevant document is executed will constitute, valid, legal and binding obligations and are enforceable in accordance with their terms.

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EXECUTED by the parties on the date first written above: