John Spiro Koudounis is an American business executive who serves as president and chief executive officer (CEO) of Calamos Investments. He was previously president and CEO of Mizuho Securities USA Inc., a subsidiary of Japanese banking and holding company Mizuho Financial Group.
Koudounis is the founder of the Chicago CEO COVID-19 Coalition. He is a member of the Leadership Council at Concordia and of the Bretton Woods Committee.
Raised in Chicago, Koudounis attended Niles West High School in Skokie, Illinois, where he was the class president. He played basketball and American football. He interned for Senator John Chafee and at Kidder Peabody, where he worked during the Black Monday stock market crash in 1987. In 1988, he graduated from Brown University in Providence, Rhode Island, earning a double major in International Diplomacy and Economics.
Koudounis began his financial career at Merrill Lynch in 1988 immediately after graduating from Brown University. He then joined ABN AMRO's North American branch, where he spent 12 years as the head of fixed income.
In 2008, Koudounis joined Mizuho Securities USA Inc. as executive managing director and head of fixed income, overseeing trading, sales, and investment banking activities. In the following year, under his leadership, the fixed income division reported record earnings for the firm. In 2010, at the age of 44, he was appointed president and CEO of the company, becoming the youngest CEO of a Wall Street firm up to that point in time.
In early 2016, Koudounis was the designated CEO of Calamos Investments, an investment firm headquartered in Naperville, Illinois. He was appointed by founder John Calamos, Sr. as part of Calamos' succession plan. Koudounis oversees the business operations of the firm.
Koudounis is the founderÃÂ of the Chicago CEO COVID-19 Coalition, an organization created in 2020 during the COVID-19 pandemic to provide relief for the city and bring Chicago's business leaders together. The coalition distributed over $1.5 million in proceeds from its televised fundraising.
KoudounisÃÂ is a member of the Leadership Council at Concordia and the Bretton Woods Committee. He is a member of the board of trustees of the National Hellenic Museum, and an executive advisory board member for the SEAL Future Foundation. He is a founding board member and executive committee member of The Hellenic Initiative. He is a member of Leadership 100 and Chairman of the Metropolis of Chicago Foundation. In 2016, he was inducted as an Archon of the Ecumenical Patriarchate in the Order of St. Andrew.
Koudounis is married to Joanne and has twin daughters, Constance and Demi.