Iliana Ongun

Primary Focus & Experience

Ms. Ongun advises both public and private companies in a wide range of industries in connection with mergers and acquisitions, including cross-border and domestic acquisitions and divestitures, joint ventures, private equity transactions and spin-offs. Ms. Ongun also advises companies and sponsors with respect to shareholder activism, takeover defense strategies and other corporate governance matters.

Some of Ms. Ongun’s recent transactions include representing:

• United States Steel in its $14.9 billion sale to Nippon Steel (2025), the successful defense of a proxy contest launched by an activist investor (2025), and the $2 billion joint venture and multiphase acquisition of Big River Steel (2021).
• Viking Holdings Ltd (Viking Cruises) in corporate governance matters and multiple capital markets transactions.
• Intralot in the carve-out acquisition of Bally’s international interactive i-Gaming business for €2.7 billion.
• H&E Rentals in its $4.8 billion agreement to be acquired by United Rentals and subsequent topping sale to Herc Holdings for $5.3 billion.
• Carrols Restaurant Group, the largest Burger King franchisee in the US, in its $1 billion take private by Restaurant Brands, the parent company of Burger King.
• Constellation Oil in its comprehensive recapitalization and liquidity event transaction.
• Veritas Capital and its portfolio company, Alion Science and Technology, in its $1.65 billion acquisition by Huntington Ingalls Industries.
• Pagaya Technologies in its acquisition of Darwin Homes, a leading proptech platform.
• ABB Inc., a technology leader in electrification and automation, on the carve-out sale of its Power Conversion division, Lineage Power Holdings Inc. for $505 million.
• Hudson Executive Investment Corp. in its $1.4 billion combination with Talkspace, a digital and virtual behavioral healthcare company.
• Cerberus Telecom Acquisition Corp. in its merger with KORE Wireless Group, Inc., a leader in Internet of Things solutions and connectivity.
• Apollo Global Management in its long-term strategic investment with The Abu Dhabi National Oil Company (ADNOC) in a real estate portfolio valued at $5.5 billion.
• Mizuho | Greenhill in connection with the $15 billion Black Hills and NorthWestern Energy merger of equals.

In addition to her publicly announced matters, Ms. Ongun represents boards and special committees of several high-profile tech companies in activism and governance matters that remain confidential.

Recognition & Accomplishments

Ms. Ongun serves as Chair of the New York City Bar Association Committee on Mergers, Acquisitions and Corporate Control Contests.

Ms. Ongun was selected to Bloomberg Law’s “They’ve Got Next: The 40 Under 40”, which acknowledges the next generation of legal leaders. She was also selected as a 2024 "Dealmaker of the Year" by The New York Law Journal. She has been repeatedly named a “Rising Star” by both Super Lawyers magazine and the New York Law Journal. Additionally, Ms. Ongun was identified as one of the "Top Women Attorneys" in the New York Metro area by The American Registry (2022).

Ms. Ongun is a frequent speaker at professional conferences and has written articles in numerous professional publications on topics relating to mergers and acquisitions and corporate governance. Ms. Ongun is also an adjunct professor at New York Law School, where she teaches a course on M&A.

Recent Publications

• Activism in the 2024 Proxy Season and Implications for 2025, in Harvard Law School Forum on Corporate Governance and Financial Regulation, March 14, 2025.
• Alignment Advance Notice Bylaw, in Harvard Law School Forum on Corporate Governance and Financial Regulation, March 3, 2025.
• Chancery Rejects Validity of “New Wave” Stockholder Agreement Terms, in Harvard Law School Forum on Corporate Governance and Financial Regulation, March 18, 2024.
• Corporate Officers Owe the Same Caremark Oversight Duties as Directors, in Harvard Law School Forum on Corporate Governance and Financial Regulation, March 5, 2023.
• 4 Key Takeaways From Del. Corporation Law Changes, in Law360, September 1, 2022.
• ESG Considerations in Project, Energy and Infrastructure Finance, in the International Comparative Legal Guide: Environmental, Social & Governance Law 2022, Second Edition.
• SPACs Fuel Hot M&A and IPO Markets – Will SEC Cool the Fire? Milbank General Counsel Blog, May 3, 2021.
• The Corporate Governance Review, U.S. Chapter, Law Business Research, London, Ninth ed. 2019 (Eighth ed. 2018, Seventh ed. 2017, Sixth ed. 2016, Fifth ed. 2015).
• ISS Announces Final 2018 Voting Policies, in Harvard Law School Forum on Corporate Governance and Financial Regulation, November 19, 2017.
• SEC Provides Guidance on Shareholder Proposals, in Columbia Law School’s Blog on Corporations and the Capital Markets, November 6, 2017.
• ISS Announces Final 2016 Voting Policies, in Harvard Law School Forum on Corporate Governance and Financial Regulation, November 24, 2015.