In a statement, the commission said Google had made “fundamental changes” to its strategy, giving its own products an advantage over its rivals in search results.
It also found that Google deliberately demoted rival products, abusing its market dominance.
The $2.7 billion fine is the commission’s largest ever against a company accused of antitrust practices. The ruling will also force Google to end its anti-competitive practices within 90 days.
The commission congratulated Google’s many innovative technologies and services, but said the company had abused its position and the trust of European consumers.
Commissioner Margrethe Vestager said: “What Google has done is illegal under EU antitrust rules. It denied other companies the chance to compete on the merits and to innovate. And most importantly, it denied European consumers a genuine choice of services and the full benefits of innovation."
Google makes almost $80 billion worldwide from Google searches.
The majority of Google’s transgressions came from its Google Shopping service, which offers comparison shopping, allowing users to compare retailers, products and prices.
According to the commission, Google’s initial attempt at this, Froogle, did not do well when it launched in 2004.
In 2008, Google made a fundamental change to its strategy, giving its own products an advantage over its rivals’.
The Commission has been investigating Google Shopping since 2010.