Mark Suster is an American entrepreneur, angel investor and investment partner at Upfront Ventures (until June 2013 known as GRP Partners). He is a prominent blogger in the startup venture capital world and mentor at Techstars, a mentorship-driven seed stage investment fund.

Suster grew up in Northern California and is a dual citizen of both the United Kingdom and the United States. He graduated from University of California, San Diego with a Bachelor of Arts in Economics. He started his career as a programmer at Accenture, which later paid for a postgraduate Master of Business Administration from the University of Chicago.

In 1999, with Ireland-based property entrepreneur Brian Moran, he founded his first company, a construction collaboration technology business called BuildOnline, where he was also chief executive officer. BuildOnline merged with US-based rival Citadon in December 2006 and the combined business, CTSpace, was acquired by the French Sword Group corporation a year later in December 2007. By this stage, Suster had already left the business, having founded a second company, a content collaboration software business, Koral. In April 2007, Koral was acquired by Salesforce.com where Suster took the role of Vice President, Product Management. He joined Upfront Ventures, an investment firm, later in 2007.

As an investor, Suster focuses on early-stage technology companies. They include: Affordit, DataSift, EagleCrest Energy, EcoMom, ExpenseCloud, Gendai Games, Osmo, MyTime, and LaughStub.