Three pay monthly customers can now browse and email without limits for £5 a day anywhere in the European Union.
The Euro Internet Pass can be bought instantly via a text link Three subscribers receive on any arrival in any supported country.
The Pass allows unlimited streaming until midnight on the day of purchase, but it doesn’t include tethering to tablets and laptops, and it doesn't cover 3G dongles or Three's MiFi portable 3G hotspot.
Thomas Malleschitz, marketing director at Three said, “We love the mobile internet at Three and we want our customers to enjoy it on holiday as much as they do at home.
“The Euro Internet Pass gives our customers the freedom to use the internet in the EU without having to think about how many megabytes or gigabytes they are using or where the nearest Wi-Fi hotspot is.
"We’ve been campaigning for lower data roaming rates and welcome the new regulation from Europe.
“These changes promote competition and allow us to offer our customers a better deal so they no longer have to worry about running up a massive bill when using the internet.”
Broadband roaming tariffs will be capped across the EU from July 1 at no more than 70 Eurocents (55p) per MB.
Other networks have also introduced cheaper roaming packages, although out-of-bundle data charges are still much higher than the Euro cap.
There’s no cap on out-of-EU roaming charges, but operators will have to send you a warning text if you use more than 50 Euros of data while travelling worldwide.