< The 2017 Tech 40

9. Don Callahan
Head of Operations and Technology
Citigroup
Last year: PNR

The historical timeline of Citigroup and its predecessors dates back to 1812. The 20th-century part of it includes industry firsts in wholesale banking (international branch openings and the negotiable certificate of deposit); operations (large-scale back-office re-engineering); and consumer services (mass distribution of both credit cards and automated teller machines). The idea that "innovation is part of our DNA," as Don Callahan says, has deep resonance at Citigroup. How the $1.8 trillion-in-assets bank has organized for the 21st century's rapid technological acceleration — its opportunities and risks — is reflected in Callahan's responsibilities. The 61-year-old head of operations and technology is also executive chair of the chief information officer council, which sets companywide technology standards, and chair of the digital governance office, which is charged with driving digital transformation across the businesses. He oversees Citigroup's global information security strategy and is a member of the growth board, whose assignment is to accelerate innovation efforts. "We are going through a digital transformation, rewiring our systems and our culture to move fast and think in an agile way," says Callahan, who before joining Citigroup in 2000 held executive positions with IBM, Morgan Stanley, and Credit Suisse. He reports to Citigroup CEO Michael Corbat.

The Citi Ventures investment arm is part of a three-pronged strategic innovation force within the bank, helping to identify, develop, and test new ideas with potential business and cultural impact. The other parts are a network of eight innovation labs and an emerging-technology team. Together they analyze more than 2,000 companies annually, selecting a handful for investment, adoption, piloting, and production. Citigroup's consumer bank has a "mobile first" focus, Callahan notes. The Citi Mobile App for iPhone was built using an agile operating model and rapid prototyping. Within its institutional business, the bank last year introduced MobilePASS, a virtual token for secure login to the CitiDirect BE global transaction platform, CitiDirect BE Mobile, and the CitiDirect BE Tablet. Client transaction value on the latter two jumped to $1.8 trillion in 2016, from $552 billion the year before. "The biggest game-changer for our industry is data, and we see it as a competitive advantage," Callahan says.

 
The 2017 Tech 40

1. Adena Friedman NASDAQ 2. Catherine Bessant Bank of America Corp. 3. Robert Goldstein BlackRock Sponsored Seeking Resilience in Gravity-defying Stock Markets Sponsored by Schroders October 20, 2025 4. Jeffrey Sprecher Intercontinental Exchange 5. Lance Uggla IHS Markit

6. Shawn Edwards & Vlad Kliatchko Bloomberg 7. David Craig Thomson Reuters 8. Michael Spencer NEX Group 9. Don Callahan Citigroup 10. Elisha Wiesel Goldman Sachs Group

11. Michael Bodson Depository Trust & Clearing Corp. 12. Terrence Duffy CME Group 13. Charles Li Hong Kong Exchanges and Clearing 14. Sean Belka Fidelity Investments 15. Chris Concannon CBOE Holdings

16. Guy Chiarello First Data Corp. 17. Steven Lieblich Citadel 18. David Rutter R3CEV 19. Blythe Masters Digital Asset Holdings 20. Alfred Spector Two Sigma Investments

21. Neil Katz D.E. Shaw Group 22. Lee Olesky Tradeweb Markets 23. Richard McVey MarketAxess Holdings 24. David Gledhill DBS Bank 25. Seth Merrin Liquidnet Holdings

26. Antoine Shagoury State Street Corp. 27. Peter Brown & Robert Mercer Renaissance Technologies 28. Lou Eccleston TMX Group 29. Peter Cherecwich Northern Trust Corp. 30. Mike Chinn S&P Global Market Intelligence

31. Chris Corrado London Stock Exchange Group 32. Neal Pawar AQR Capital Management 33. Gary Norcross Fidelity National Information Services 34. Steven O'Hanlon Numerix 35. Sebastián Ceria Axioma

36. Brian Conlon First Derivatives and Kx Systems 37. Tyler Kim MaplesFS 38. Michael Cooper BT Radianz 39. Robert Schifellite Broadridge Financial Solutions 40. Jim Minnick eVestment