Professor of Practice, Georgia Institute of Technology, School of Cybersecurity and Privacy

Mary Ellen Callahan is an American attorney cybersecurity and privacy expert who also served as the Assistant Secretary for the Department of Homeland Security (DHS) Countering Weapons of Mass Destruction (CWMD) Office from August 2023 to January 2025. She was previously the chief of staff to DHS Deputy Secretary John Tien from 2021-2023, and served as DHS Chief Privacy Officer from 2009-2012.

Callahan started her practice at Hogan & Hartson (now Hogan Lovells) from 1997 to 2009, where she counseled online companies, trade associations, and other corporations on privacy, consumer protection, and litigation matters. 

In 2009, Callahan was appointed by Secretary Janet Napolitano to serve as DHS Chief Privacy Officer. Callahan led department-wide programs on privacy protections and information sharing, led all privacy initiatives in the DHS cybersecurity arena, and represented DHS in extensive outreach and negotiations with privacy counterparts in the European Union, Canada and other countries to explain and support the U.S. privacy framework.

From 2012 to 2017, Callahan was a Partner at Jenner & Block, at which she founded and chaired the firm's Privacy and Information Governance Practice. At Jenner, Callahan applied her unique and broad experience to advise an array of clients across a spectrum of industries on issues at the interface of privacy protection with cybersecurity and national security.

From 2017 to 2021, Callahan worked as an Assistant General Counsel for The Walt Disney Company. At Disney, Callahan was a leader of the global Privacy-Legal team across all segments of the company's businesses and developed crucial and innovative privacy programs and frameworks to protect the company.

In August 2023, she became the Assistant Secretary for the DHS Countering Weapons of Mass Destruction (CWMD) Office, leading the Department's efforts and coordinated with domestic and international partners to safeguard the United States against CBRN threats.  In response to President Biden's Executive Order (E.O.) 14110 on Safe, Secure, and Trustworthy Development and Use of Artificial Intelligence, CWMD wrote and released a first-of-its kind report evaluating the potential for AI to be misused to enable the development of production of CBRN threats, while also considering the benefits and application of AI to counter them.  Callahan resigned as Assistant Secretary on January 20, 2025.

Callahan is a 1990 Bachelor of Philosophy graduate from the University of Pittsburgh Honors College and College of Arts and Sciences.  She served from 2009-2022 as a Trustee on the Pitt Board of Trustees, including as Vice Chair from 2020-2021, and (Acting) Chair from 2021-2022.  She is also a graduate of the University of Chicago Law School.