Roaming charges don't exist within the EU anymore. As of midnight, you can use your phone to call or text in any EU country for the same cost you would at home.
Data allowances will vary depending on what operator you are with, but are said to be "very generous." Vodafone has become the first provider to announce its customers will have the same data allowance that they would at home.
Under the improved rules, data allowances can be restricted to as little as 3GB per month, but officials have fought hard to get astronomical charges brought right down.
The final hurdle was cleared for roaming charges to be scrapped back in January, when the European Parliament agreed a deal to cap the prices which telecoms operators pay for using each other's networks.
European officials say it's "one of the greatest and most tangible successes of the EU".
It's not clear what will happen when Britain leaves the EU, and if the government there will come up with some sort of a deal to keep charges for visitors like tourists and business people as low as other countries in Europe.