Google has been fined a record €4.34bn ($5bn; £3.9bn) over Android.
The European Commission said the firm had used the mobile operating system to illegally “cement its dominant position” in search.
The firm’s parent Alphabet has been given 90 days to change its business practices or face further penalties of up to 5% of its average global daily turnover.
It has said it plans to appeal.
However, it could easily afford the fine if required – its cash reserves totalled nearly $103bn at the end of March.