https://wccftech.com/whatsapp-for-android-now-supports-fingerprint-unlock/

At this point, a lot of people worldwide use WhatsApp as their main texting app. Needless to say, this makes WhatsApp host to a lot of personal information. Apple users have had the option to lock down their WhatsApp and use Face ID as an additional authentication method. Android users, on the other hand, have no such luck.  Currently, one has to rely on third-party apps to prevent unauthorized people from accessing WhatsApp on your device. This changes as of today, as WhatsApp users on Android can lock their conversations behind a fingerprint. According to WhatsApp's official blog post:

Earlier this year, we rolled out Touch ID and Face ID for iPhone to provide an extra layer of security for WhatsApp users. Today we’re introducing similar authentication, allowing you to unlock the app with your fingerprint, on supported Android phones. To enable it, tap Settings > Account > Privacy > Fingerprint lock. Turn on Unlock with fingerprint, and confirm your fingerprint.