Ken Siegel is the managing partner of Morrison Foerster’s Tokyo office and the head of the office’s 50-attorney M&A team. Ken’s practice focuses on the representation of high-technology companies in acquisitions, joint ventures, and strategic alliances.
Ken has been consistently ranked as one of the leading U.S. attorneys in Japan. Among other things, he is the only attorney rated as a “Star Individual” for M&A in Japan (the level above Band 1) by Chambers Global, having been ranked at this level for more than a dozen years (2011–2024 editions). According to Chambers Asia-Pacific, Ken is “commercial and pragmatic, an incredible M&A attorney” who “deserves tremendous credit for his M&A practice” and has “outstanding acumen, experience and leadership.”
In 2022, Ken was recognized by the Financial Times – receiving their Innovative Lawyers Award, as one of the most innovative attorneys in the Asia Pacific region. He has also been recognized multiple times as in the American Lawyer – including as “Dealmaker of the Week” for his work on Hitachi’s $5 billion sale of its hard disk-drive business to Western Digital as well as for representing SoftBank in its $21.6 billion acquisition of Sprint, a transaction that was named the Global M&A Deal of the Year by The American Lawyer.
Ken received his B.A. magna cum laude from Amherst College. He studied Japanese language at Stanford University’s Inter-University Center for Japanese Language in Tokyo and at the Johns Hopkins University’s School of Advanced International Studies (SAIS), receiving a graduate degree in International Affairs. He received his J.D. degree from the University of Chicago Law School.
Select Rankings
Ken’s recent notable awards include:
Most Innovative Legal Practitioner in Asia-Pacific (Financial Times Innovative Lawyers Award 2022)
- Star Individual for Japan: Corporate/M&A (Chambers Global 2024)
- Star Individual for Japan: Corporate/M&A (Chambers Asia-Pacific 2024)
- Hall of Fame for Japan: Corporate and M&A (The Legal 500 Asia Pacific 2024)
- Market Leader for Japan: M&A (IFLR1000 2024)
- Corporate, M&A Law, Private Equity, Private Funds and Venture Capital Law [The Best Lawyers in Japan (Recognized since 2009)]
- Foreign Lawyer of the Year (Asian Legal Business (ALB) Japan Law Awards 2018)
- Tokyo Managing Partner of the Year (Asian Legal Business (ALB) Japan Law Awards 2017)
Experience
SoftBank in connection with its proposed $6.5 billion acquisition of Ampere Computing, an American fabless semiconductor company developing processors for large-scale compute environments.
SoftBank, in connection with multiple investments in OpenAI, America’s premier artificial intelligence (AI) company and developer of the transformational large language models that are driving the AI revolution, including its proposed up to $40 billion investment in OpenAI.
SoftBank on The Stargate Project, including the formation of a new joint venture between SoftBank and OpenAI as lead partners, to invest billions of dollars in new AI infrastructure in the United States.
SoftBank in connection with its investment in Tempus AI and the establishment of a Japan joint venture, SB TEMPUS Corp. with Tempus AI, Inc., to expand Tempus’s leading AI solutions for medical applications to Japan and Southeast Asia.
Arm Holdings plc in its $5.2 billion initial public offering and listing on Nasdaq, the largest global IPO of 2023.
SoftBank in its $280 million Series E investment in Mapbox, an AI-powered location services platform fueling navigation technology used by Toyota, General Motors and BMW.
The board of Toshiba Corporation in its $15 billion take-private, the largest take-private transaction in Japanese history.
SoftBank in its sale of 90.01% stake in Fortress, a global investment manager with over $45 billion in assets under management, to Mubadala.
SoftBank in its $375 million acquisition of Berkshire Grey, Inc. (Nasdaq: BGRY), a robotic automation company, as well as interim financing through the completion of the merger.
SoftBank, Sprint’s controlling shareholder, on the landmark merger of Sprint and T-Mobile US, Inc., with a total implied enterprise value for Sprint of $59 billion and an aggregate implied enterprise value for the combined company of $146 billion.