Hundreds of people reported problems with the popular messaging app on the morning.
Users around the world are experiencing issues with WhatsApp, according to website health tracker Down Detector.
Europe is the worst affected region, though parts of Asia and South America also face severe disruption.
It is the latest in a series of outages to hit the Facebook-owned app, with a major incident in March last year leaving users cut off for nearly an entire day.
More than 500 million people use the app each day and many have taken out their frustrations across Twitter and Facebook.
A report earlier this month revealed that WhatsApp is the worst-hit platform for internet shutdowns.
The app suffered 6,236 hours of deliberate disruption in 2019, largely as a result of authoritarian governments blocking access to it.
The app's secure encryption and vast user base make it popular among protesters who want to evade authorities during periods of civil unrest.
