Frederick Ryan Castillo is a partner in Mayer Brown’s New York office and a member of the Capital Markets practice. His work focuses on securities and corporate finance transactions. Ryan advises issuers, investment banks and sponsors in connection with public offerings and private placements of debt, equity and hybrid securities, including initial public offerings, follow-on offerings, investment grade and high-yield debt offerings, private investment in public equity, tender and exchange offers, consent solicitations, medium-term note programs and other capital markets transactions in the United States, Canada and the Euro markets. He represents companies and financial intermediaries involved in a broad range of industries, including financial services, technology, telecommunications, retail, life sciences, real estate and energy. He also advises clients on corporate governance, securities law compliance and general corporate matters.

The Legal 500 US 2023 ranks Ryan as a “Next Generation Partner” for Capital Markets: Debt Offerings, calling him an “emerging talent,” and also recommends him for Capital Markets: Global Offerings and for Capital Markets: High-Yield Debt Offerings. IFLR1000 2022 names him a “Rising Star Partner” for Capital Markets: Debt and Capital Markets: Equity in the United States. He was ranked as a “Rising Star” for the same categories by IFLR1000 2021, 2020, and 2019. Euromoney recognized Ryan as a “Rising Star” in the capital markets category at its 2020 Rising Stars Americas Awards. He is named a “Rising Star” for the Americas in the Capital Markets category in Euromoney’s Expert Guides: Rising Stars in 2022 and 2021. Ryan is recognized by Best Lawyers: Ones to Watch 2021 for his work in Securities and Capital Markets law in the United States.

Ryan is co-author of A Deep Dive Into Capital Raising Alternatives (2020) and author of Non-GAAP Explained (2017), both published by the International Financial Law Review. He regularly writes on securities law issues and has authored a number of capital markets-related thought leadership pieces, including articles published by LexisNexis, Thomson Reuters, The Business Lawyer and the Harvard Business Law Review. Ryan serves as an adjunct professor at the George Washington University School of Law, where he teaches a course on securities regulation.

Ryan earned his Master of Laws degree with a concentration in international finance from Harvard Law School, where he served as editor of the Harvard Business Law Review. He earned his JD with honors from the Ateneo de Manila Law School, where he served as captain of the World Champion team in the 45th Philip C. Jessup International Law Moot Court Competition. He holds a BA in Economics, with honors, from the Ateneo de Manila University. Ryan previously worked in the capital markets group of another global law firm in New York. Prior to that, he worked in a regional law firm in Singapore, where he advised clients on capital markets and cross-border transactions across the Asia-Pacific.


Ateneo de Manila University, BA, with honors

Ateneo de Manila University, JD, with honors
Captain of the World Champion team in the 45th Philip C. Jessup International Law Moot Court Competition

Harvard Law School, LLM
Editor, Harvard Business Law Review


  • New York
  • Philippines