O’Melveny Worldwide

Paul Sieben, Head of O’Melveny’s Silicon Valley office, represents all stages of technology companies as well as numerous venture capital firms, other investors and market participants. Paul’s practice is focused on M&A, venture capital, private equity, early liquidity transactions, spin-offs, recapitalizations, public equity offerings and private debt transactions. Paul has served as lead counsel on more than 1,000 venture capital, angel and private-equity financings, more than 200 M&A transactions of all sizes, and a significant number of recapitalizations, public offerings and other transactions — many on behalf of, or opposite, major tech companies, venture capital and private equity firms.

Paul’s practice stems from his relationships with a combination of early and late stage venture capital firms, large public technology companies and from his startup company practice, where he handles formation, founder-related matters, seed investments and venture capital financings for early-stage companies and then continues to represent them in various matters including later stage financings, M&A and corporate governance matters as they grow into larger private and public companies.

His clients include companies in a wide range of technology markets, including fintech and crypto, security, software, autonomous vehicles, storage, gaming, cloud, big data and AI, media, social, clean technology, healthtech and biotech. Paul also has significant cross-border experience.

Paul has been recognized by several publications for his work, including, Best Lawyers (which has listed Paul one of the Best Lawyers in America 2023), the International Financial Law Review 1000 (which has named Paul one of its leading lawyers for private equity), The Legal 500 US (which has recognized him as a leading lawyer in its Venture Capital and Emerging Companies category, citing the “extraordinary support” he provides to clients and his ability to “produce very high-quality work on short timelines”) and Super Lawyers’ “Rising Stars” list of Northern California’s best young attorneys in the area of Mergers & Acquisitions.

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  • US$800 million financing and related tender offer of private social media company
  • Over US$1.0 billion spinout and sale of mobile gaming company
  • US$200 million financing of a leading mobile payments company
  • US$200 million acquisition of advanced authentication company
  • Scores of private company tender offer and other “early liquidity” transactions on behalf of both investors and large private technology companies
  • Formation, financing and ultimate sales of multiple social media, cyber-security, e-commerce and enterprise software companies to the world’s largest public and private Internet and software companies
  • Spin-out, financing, public offering and sale of authentication device and software provider 
  • Private-equity buyouts of international and domestic data center switching, health-care services, solar and telecommunications companies 
  • Multiple joint venture transactions involving clean technology companies 
  • US$350 million sale of private data-loss prevention company
  • Multiple Nasdaq public offerings of flash memory companies
  • Nasdaq initial public offering of a U.K. automation company
  • Multiple PIPE transactions and Nasdaq public offerings for storage and data backup company


Bar Admissions

  • California


  • University of California, Los Angeles, J.D., 1998: Order of the Coif; Corpus Juris Secundum Awards in Tort Law and Civil Procedure
  • University of California, Santa Barbara, B.A., 1995: High Honors; Dean’s List

Honors & Awards

  • Recognized by Best Lawyers® for Mergers and Acquisitions Law in Menlo Park, CA (2023-2024)
  • International Financial Law Review 1000, Leading Lawyers for Private Equity
  • The Legal 500 US, Recommended in Venture Capital and Emerging Companies Category
  • The Legal 500 US, Recommended in M&A - Middle-Market Category
  • Super Lawyers’ “Rising Stars” Northern California, Mergers & Acquisitions

Professional Activities


  • California Bar Association


  • Finding Genius Fall Venture Capital Forum
  • JLABS Legal Webinar Series for Life Sciences Entrepreneurs, “Raising Capital: A Legal Primer”
  • Emerging Manager Venture Summit, “Managing Partial Liquidity –  A Map through the Minefield”
  • Silicon Valley Association of General Counsel (SVAGC): “Trends in Technology Mergers & Acquisitions”
  • Dow Jones VentureWire Technology Showcase, “Finding an Exit”; VentureBeat, “Downturn Roundtable”
  • Entrepreneurs Forum, North America Chinese Semiconductor Association (NACSA)