Final answer:
The EU law passed in 2018 that required companies to promptly report personal data breaches is called GDPR.
Step-by-step explanation:
The EU law passed in 2018 that required companies to promptly report personal data breaches was called the General Data Protection Regulation (GDPR). This law was implemented by the European Union to provide comprehensive protection to individuals by placing strict restrictions on the collection and processing of personal data.