Exhibit 99.1

10 October 2025

MAC Copper Limited Announces Scheme with Harmony becomes effective

ST. HELIER, Jersey – (BUSINESS WIRE) – MAC Copper Limited ARBN 671 963 198 (NYSE:MTAL; ASX:MAC)

MAC Copper Limited (NYSE:MTAL, ASX:MAC) (“MAC” or the “Company”) is pleased to announce that it has today lodged with the Jersey Registrar of Companies a copy of the order of the Royal Court of Jersey (the “Court”) sanctioning the proposed acquisition of 100% of the issued share capital in MAC by Harmony Gold (Australia) Pty Ltd (a wholly owned subsidiary of Harmony Gold Mining Company Limited (JSE:HAR, NYSE:HMY)) (“Harmony”) by way of a Jersey law scheme of arrangement pursuant to Article 125 of the Companies (Jersey) Law 1991 (as amended) (“Scheme”).

As a result, the Scheme is now legally effective. A copy of the Court’s order as lodged with Jersey Registrar of Companies is attached to this announcement.

Capitalised terms used in this announcement have the meaning given to them in the Scheme Circular, a copy of which is attached to MAC’s announcement released on 31 July 2025.

Suspension of trading

MAC CDIs will be suspended from trading on the ASX with effect from close of trading today, 10 October 2025.

Today will also be the last day of dealings in MAC Shares on the NYSE.

Scheme Consideration

MAC Securityholders who hold MAC Shares or MAC CDIs at the Scheme Record Date, being 7:00 pm (Sydney time) on 17 October 2025 (for MAC CDI Holders) or 5:00 pm (New York time) on 17 October 2025 (for Scheme Shareholders) will be paid the Scheme Consideration in accordance with the terms of the Scheme. It is anticipated that the Scheme will be implemented on 24 October 2025.

Indicative Scheme timetable

The remaining key dates expected for the Scheme are set out below.

Event	Date and time (Jersey time)
Effective Date	10 October 2025
Last day of dealings in MAC CDIs on the ASX¹	10 October 2025 (close of trading on the ASX)
Last day of dealings in MAC Shares on the NYSE²	10 October 2025 (close of trading on the NYSE)
Suspension of quotation of MAC CDIs on the ASX	13 October 2025 (before trading opens on the ASX)
Initiate delisting of MAC Shares from the NYSE³	14 October 2025 (before trading opens on the NYSE)
Scheme Record Time	5:00 pm (New York time) on 17 October 2025 for Scheme Shareholders 7:00 pm (Sydney time) on 17 October 2025 for MAC CDI Holders
Complete delisting of MAC Shares from the NYSE	24 October 2025
Implementation Date	24 October 2025

Consideration payment date to DTC for further payment by DTC participants to beneficial owners holding MAC Shares within DTC	27 October 2025
Consideration payment date for MAC Shares held outside DTC	31 October 2025
Consideration payment date for MAC CDIs	31 October 2025
Delisting of MAC from the ASX	3 November 2025

¹MAC CDI Holders may sell their MAC CDIs on the ASX until ASX market close on October 10, 2025 (at which point the ASX is expected to halt and suspend trading in MAC CDIs before start of trade on ASX on October 13, 2025).

²Shareholders may sell their MAC Shares on the NYSE until NYSE market close on October 10, 2025 (at which point the NYSE is expected to halt and cease trading in MAC Shares).

³NYSE files a Delisting Application (Form 25-NSE) with the SEC.

Further information

If, after reading the Scheme Circular, you have any questions about the payment of the Scheme Consideration, please contact MAC’s Share Registry or CDI Registry (as applicable), at:

If you are a MAC Shareholder
Call toll-free in US:
+1 (800) 662-5200
Outside of US:
+1 (203) 658-9400

If you are a MAC CDI Holder
Within Australia:
1300 229 418
Outside Australia:
+61 2 9066 4059

– Ends –

This announcement has been authorised for release by Mick McMullen, CEO and Director.

Contacts

Mick McMullen

Chief Executive Officer & Director

MAC Copper Limited

investors@metalsacqcorp.com

Morné Engelbrecht

Chief Financial Officer

MAC Copper Limited

About MAC Copper Limited

MAC Copper Limited (NYSE:MTAL; ASX:MAC) is a company focused on operating and acquiring metals and mining businesses in high quality, stable jurisdictions that are critical in the electrification and decarbonization of the global economy.

MAC Copper Ltd 6-K