The HSE's 'COVID Tracker' contact tracing app has now been installed by one million people.
The app became available for iOS and Android devices on Monday evening.
HSE boss Paul Reid this evening confirmed the app has already reached one million registered users, less than 48 hours after it became widely available.
A number of other countries in Europe and around the world have introduced similar contact tracing apps in recent weeks and months.
However, Mr Reid earlier today called the Irish launch "by far the most successful launch" of any contact tracing app anywhere in the world.
COVID Tracker's main function is to let users know when they've been in close contact with someone who later tests positive for COVID-19.
The app uses Bluetooth technology to register any other devices nearby, with the Government insisting privacy is "right at the heart" of the design.