Rubicon Project is an online advertising technology firm based in Los Angeles, California.

The company was founded in 2007 by Frank Addante, Craig Roah, Duc Chau and Julie Mattern, who had previously worked together at L90, an online advertising network.

By April 2009, the company had raised $33 million in venture funding led by Clearstone Venture Partners, IDG Ventures Asia and Mayfield Fund. The company also secured $8 million in venture debt from Silicon Valley Bank.

In February 2017, the company released its president and several other top executives.

On March 14, 2017, CEO and founder Frank Addante stepped down from his position to take the role of chairman. The company announced Michael Barrett, previously the chief executive of mobile advertising marketplace Millennial Media and chief revenue officer at Yahoo!, would be the new chief executive.

In September 2009, the company acquired OthersOnline, an audience profiling technology company based in Seattle.

In May 2010, the company bought Site Scout, a malware detection company also based in Seattle.

In October 2010, the company acquired Fox Audience Network from News Corp. in return for a minority stake in the company. It also received $18 million in additional funding led by Peacock Equity, the venture division of NBC Universal.

In May 2012, the company acquired Mobsmith, a mobile technology company.

In August 2012, the company became the top-ranked online advertising company in terms of reach, with a 96.2% audience share, according to rankings provided by ComScore. This placed Rubicon ahead of Google for the first time, and also ahead of other competitors such as AOL and AT&T.

In July 2013, the company expanded its executive ranks with the addition of 10 senior people.

In February 2014, the company filed for an IPO and went public in April 2014 opening at over $20 per share. The stock fell back to about $16 per share later in the month.

In March 2014, the company was named number two on the top Ad Exchange Entities by comScore.