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CEO of Calamos Investments


John S. Koudounis is one of today’s most prominent leaders in the banking and investment fields. He has earned the distinction of being the youngest Chief Executive Officer (CEO) on Wall Street during his tenure as the head of Mizuho Securities USA, Inc., a subsidiary of Japanese holding company Mizuho Financial Group.

As a highly sought after business executive, Koudounis was recently appointed CEO of Calamos Investments. He regularly appears as a commentator on such financial news programs as Fox Business, CNBC, CNN, Bloomberg Television, and many others.

Koudounis was raised in Chicago, Illinois, and Forbes journalist Antoine Gara describes him as a “gregarious Chicagoan of Greek descent.” His grandparents emigrated from Sparta, Greece in 1900 and sold hot dogs outside of Wrigley Field. His father, George, eventually expanded the family business by opening a drive-in called George’s Old Town Red Hots.


Koudounis attended Niles West High School in Skokie, where he was class president and played basketball and football. He was awarded several scholarships for football and ultimately chose to attend Brown University in Providence, Rhode Island.

At Brown, Koudounis double-majored in International Diplomacy & Foreign Affairs and Economics, while playing football. He also interned for the late Senator John Chafee and for U.S.-based securities firm, Kidder, Peabody & Company. After graduating in 1988, Koudounis began his financial career with Merrill Lynch. Later, he worked for ABN AMRO North America as the company’s head of fixed income for twelve years.

In 2010, Koudounis became the youngest CEO of any Wall Street firm when he was appointed President/CEO of Mizuho Securities USA Inc. at age 44. He was responsible for the firm’s activities in trading, sales, and investment banking. As well as having direct management responsibilities in the Americas, he served on Mizuho’s global management team in Tokyo. During Koudounis’ leadership of Mizuho USA, his department annually exceeded the entire firm’s financial expectations.

Koudounis is a board member of the National Hellenic Museum and the Hellenic Initiative. He is also a Leadership Council Member of the Concordia Summit. He is married to Joanne and has twin daughters, Constance and Demi.

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