Don Callahan bought C once, on Feb 11, 2016

Daniel “Don” Callahan is a corporate director and former Chief Administrative Officer and Global Head of Operations, Technology and Shared Services at Citigroup Inc. (C), where he served as the bank’s Head of Operations and Technology from 2007 until his retirement in December 2018.( In that role he oversaw complex global businesses and services in more than 100 countries, a multi‑billion‑dollar operating budget, and Citigroup’s critical systems infrastructure, including major cyber‑security and digital‑transformation initiatives.(

Prior to joining Citi, Callahan held senior executive positions at Morgan Stanley and Credit Suisse, following a 12‑year tenure at IBM that included serving as Director of Strategy for IBM Japan.( Since leaving Citi he has become Founder & CEO of Callahan Advisors LLC and an Executive Partner at Bridge Growth Partners, and serves on multiple public and private company boards, including Scotiabank, WEX, Kore.ai, and others.( Callahan holds a B.A. in History from Manhattanville College, where he has served as Trustee Chair Emeritus, and he remains active in educational and cultural institutions through board and advisory roles.(

Written by Perplexity from public sources.