HUN Huntsman Corporation

Filing pursuant to Rule 425 under the

Securities Act of 1933, as amended

Filer: Clariant Ltd

Subject Company: Huntsman Corporation

Commission File Number: 001-32427

Merger Team Meets to Get Ready for Day 1

In the first week of September, the Merger Management Team gathered for another meeting in The Woodlands, Texas, for joint Huntsman-Clariant working groups which, this time, worked on details for operational procedures for and phases after the closing.

Another step towards the successful closing of the merger that is expected to occur December 2017 / January 2018 was taken in the first week of September, when the Merger Management Team gathered again in The Woodlands, Texas. This time, the working groups comprised of equal numbers of representatives from both companies focused on planning the HuntsmanClariant organizational setup and agreeing operational procedures for the phases after closing the merger.

Detailed planning for Day 1 and beyond

More detailed planning included the steps that have to be taken for “day 1 readiness” — the first day after the closing of the merger — and for day 100 and day 365. While legal and regulatory aspects are the main issues for day 1 readiness, the phase of the first one hundred days will put emphasis on the operations under HuntsmanClariant structure and the new organization in order to leverage synergy opportunities in the best possible way. For the first year as a joint company, performance enhancement and further planning will be the main strategic issues.

Issues with key relevance for day 1 readiness, for example, are IT and communications. To prepare, experts from IT and Communications are currently looking into how a common IT and communication infrastructure should be set up in the transition phase and beyond in order to ensure business continuity. “In this phase we look into the respective IT infrastructures and define the best, fastest, and most valuable solutions for our future organization” said Volker Laska , Head of Group IT. “We will ensure a seamless transition to the new company” .

Kai Rolker , Head of Group Communications, added: “Communication will be key for the successful launch of HuntsmanClariant. In order to keep employees and customers informed about all relevant steps until and beyond the closing of the merger we will take care of frictionless functioning of our intranet and internet solutions.”

The work conducted during the first week of September in The Woodlands will serve as the basis for further planning and an upcoming workshop at the end of September that will look into interdependencies and further preparation of day 1 readiness.

Stay tuned for another merger update later this month/beginning of October with more details on the future organizational set-up.

Further information on the merger can be found on the Insite page entitled “HuntsmanClariant Merger Information.”

Cautionary Statement Regarding Forward-Looking Statements

This communication contains certain statements that are “forward-looking statements” within the meaning of Section 27A of the Securities Act of 1933, as amended (the “Securities Act”), and Section 21E of the Securities Exchange Act of 1934, as amended.  Clariant Ltd (“Clariant”) and Huntsman Corporation (“Huntsman”) have identified some of these forward-looking statements with words like “believe,” “may,” “could,” “would,” “might,” “possible,” “will,” “should,” “expect,” “intend,” “plan,” “anticipate,” “estimate,” “potential,” “outlook” or “continue,” the negative of these words, other terms of similar meaning or the use of future dates. Forward-looking statements in this communication include, without limitation, statements about the anticipated benefits of the

contemplated transaction, including future financial and operating results and expected synergies and cost savings related to the contemplated transaction, the plans, objectives, expectations and intentions of Clariant, Huntsman or the combined company, the expected timing of the completion of the contemplated transaction. Such statements are based on the current expectations of the management of Clariant or Huntsman, as applicable, are qualified by the inherent risks and uncertainties surrounding future expectations generally, and actual results could differ materially from those currently anticipated due to a number of risks and uncertainties. Neither Clariant nor Huntsman, nor any of their respective directors, executive officers or advisors, provide any representation, assurance or guarantee that the occurrence of the events expressed or implied in any forward-looking statements will actually occur. Risks and uncertainties that could cause results to differ from expectations include: uncertainties as to the timing of the contemplated transaction; uncertainties as to the approval of Huntsman’s stockholders and Clariant’s shareholders required in connection with the contemplated transaction; the possibility that a competing proposal will be made; the possibility that the closing conditions to the contemplated transaction may not be satisfied or waived, including that a governmental entity may prohibit, delay or refuse to grant a necessary regulatory approval; the effects of disruption caused by the announcement of the contemplated transaction making it more difficult to maintain relationships with employees, customers, vendors and other business partners; the risk that stockholder litigation in connection with the contemplated transaction may affect the timing or occurrence of the contemplated transaction or result in significant costs of defense, indemnification and liability; ability to refinance existing indebtedness of Clariant or Huntsman in connection with the contemplated transaction; other business effects, including the effects of industry, economic or political conditions outside of the control of the parties to the contemplated transaction; transaction costs; actual or contingent liabilities; disruptions to the financial or capital markets, including with respect to the financing activities related to the contemplated transaction; and other risks and uncertainties discussed in Huntsman’s filings with the U.S. Securities and Exchange Commission (the “SEC”), including the “Risk Factors” sections of Huntsman’s annual report on Form 10-K for the fiscal year ended December 31, 2016 and the quarterly report on Form 10-Q for the six month period ended June 30, 2017. You can obtain copies of Huntsman’s filings with the SEC for free at the SEC’s website (www.sec.gov). Forward-looking statements included herein are made only as of the date hereof and neither Clariant nor Huntsman undertakes any obligation to update any forward-looking statements as a result of new information, future developments or otherwise, except as expressly required by law. All forward-looking statements in this communication are qualified in their entirety by this cautionary statement.

Important Additional Information and Where to Find It

NO OFFER OR SOLICITATION

This communication is not intended to and does not constitute an offer to sell or the solicitation of an offer to subscribe for or buy or an invitation to purchase or subscribe for any securities or the solicitation of any vote or approval in any jurisdiction, nor shall there be any sale, issuance or transfer of securities in any jurisdiction in contravention of applicable law. No offer of securities will be made except by means of a prospectus meeting the requirements of Section 10 of the Securities Act.

IMPORTANT ADDITIONAL INFORMATION WILL BE FILED WITH THE SEC

In connection with the contemplated transaction, Clariant intends to file a registration statement on Form F-4 with the SEC that will include the Proxy Statement/Prospectus of Huntsman. The

Proxy Statement/Prospectus will also be sent or given to Huntsman stockholders and will contain important information about the contemplated transaction. INVESTORS AND SHAREHOLDERS ARE URGED TO READ THE PROXY STATEMENT/PROSPECTUS AND OTHER RELEVANT DOCUMENTS FILED OR TO BE FILED WITH THE SEC CAREFULLY WHEN THEY BECOME AVAILABLE BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION ABOUT CLARIANT, HUNTSMAN, THE CONTEMPLATED TRANSACTION AND RELATED MATTERS. Investors and shareholders will be able to obtain free copies of the Proxy Statement/Prospectus (when available) and other documents filed with the SEC by Clariant and Huntsman through the website maintained by the SEC at www.sec.gov.

PARTICIPANTS IN THE SOLICITATION

Huntsman and its directors and executive officers may be deemed to be participants in the solicitation of proxies from Huntsman investors and shareholders in connection with the contemplated transaction. Information about Huntsman’s directors and executive officers is set forth in its proxy statement for its 2017 Annual Meeting of Stockholders and its annual report on Form 10-K for the fiscal year ended December 31, 2016. These documents may be obtained for free at the SEC’s website at www.sec.gov. Additional information regarding the interests of participants in the solicitation of proxies in connection with the contemplated transactions will be included in the Proxy Statement/ Prospectus that Huntsman intends to file with the SEC.