The Data Protection Commission, which acts as the lead supervisory authority for Google in the European Union, said its probe would examine whether Google's processing of data in advertising transactions breaches the bloc's privacy rules.
"A statutory inquiry pursuant to section 110 of the Data Protection Act 2018 has been commenced in respect of Google Ireland Limited's processing of personal data in the context of its online Ad Exchange," the regulator said in a statement Wednesday.
A Google spokesperson said, "We will engage fully with the DPC's investigation and welcome the opportunity for further clarification of Europe's data protection rules for real-time bidding. Authorized buyers using our systems are subject to stringent policies and standards."
Brussels last year introduced sweeping new privacy reforms known as the General Data Protection Regulation, or GDPR, which gave Europeans new powers in how they can control their data. Such powers include the right to find out how companies use their data, as well as the ability to force firms to destroy their data.
It comes as tech companies face heightened regulatory scrutiny worldwide over everything from hateful content to data protection. Last year saw Facebook in particular hit with much criticism over how it allowed controversial political consultancy Cambridge Analytica to get access to the data of 87 million users.
Meanwhile, Google was fined 50 million euros ($56 million) earlier this year by France's privacy regulator, in the first penalty for a U.S. tech giant since the EU's GDPR law was introduced.
The launch of Ireland's inquiry into Google comes days before the first anniversary of GDPR, which came into effect on May 25, 2018.
- CNBC's Elizabeth Schulze contributed to this report.