He purchased the National Hockey League’s Florida Panthers for $250m in September of 2013. 
In December of 2016 he was nominated by President-elect Donald Trump to be the next Secretary of the Army, but he withdrew his nomination in February 2017 after distancing himself from his business ties proved too difficult, according to two Trump administration officials.
His net worth is estimated at $2.3 billion, according to the Bloomberg Billionaires Index.
Viola began his career as a member of the New York Mercantile Exchange (NYMEX). He later served as director of NYMEX from 1987 to 1990, vice chairman from 1993 to 1996, and chairman from 2001 to 2004. He helped lead NYMEX's recovery after the September 2001 terrorist attacks, airlifting generators to the Nymex building in lower Manhattan and ferrying traders across the Hudson River from New Jersey so trading could resume less than a week after the attacks.
In 2001, Viola was instrumental in founding the Combating Terrorism Center at West Point.  Under Viola's leadership, NYMEX launched the Clearport facility for clearing energy derivatives traded in the OTC markets in 2002.
In 1987, he launched Pioneer Futures as a futures commission merchant. Later, Pioneer became a division of Man Financial, which later became MF Global. In 1988, Viola funded The Independent Bank Group in Texas. In 1989, Viola started a company now known as Mako Group, which is the independent derivatives market maker in Europe. Viola served as a member of National Petroleum Council from 2002 to 2004. 
Viola is also chairman and chief executive officer of Virtu Financial LLC, the company he founded in 2008.
Viola was the founder and a director of Pioneer Futures, a futures commission merchant. Pioneer offered clearing and execution services for introducing brokers, individual traders, and institutional investors, including CTAs and managed futures accounts. Pioneer in 2013 became an Introducing Broker.
He also founded the market making firm Madison Tyler with David Salomon in 2002 and later merged it with Virtu.
Viola serves as vice-chairman of the National Italian American Foundation board of directors and vice chairman of both the New Jersey Nets and Brooklyn Sports Ownership Group.
Viola is a graduate of the United States Military Academy at West Point and achieved the rank of major in the United States Army Reserves. In 1983, he graduated from New York Law School with a juris doctor degree.
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