DoubleClick is a subsidiary of Google that develops and provides Internet ad serving services. Its clients include agencies, marketers (Universal McCann Interactive, AKQA etc.) and publishers who serve customers like Microsoft, General Motors, Coca-Cola, Motorola, L'Oréal, Palm, Inc., Apple Inc., Visa USA, Nike, Carlsberg among others. DoubleClick's headquarters is in New York City, United States.

DoubleClick was founded in 1995 by Kevin O'Connor and Dwight Merriman. It was formerly listed as "DCLK" on the NASDAQ, and was purchased by private equity firms Hellman & Friedman and JMI Equity in July 2005. In March 2008, Google acquired DoubleClick for US$3.1 billion. Unlike many other dot-com companies, it survived the bursting of the dot-com bubble. Today, it focuses on uploading ads and reporting their performance.

DoubleClick was founded as one of the earliest known Application Service Provider (ASP) for internet "ad-serving", primarily banner ads. After an IPO on the NASDAQ under the "DCLK" ticker symbol in early 1998, the company was inappropriately associated with an internet traffic report including Yahoo!, AOL, Alta Vista and Excite where the company was listed within the top 10 internet websites in the world -- when in fact it was delivering as many ad impressions at the time as these early major internet properties were delivering page views. Its DoubleClick DART (Dynamic Advertising Reporting & Targeting) ASP/SaaS ad-serving technology was second-to-none, allowing clear targeting & reporting of ad-serving per media property for websites within its network and technology sectors.