When crossing borders between countries in Europe, do you need a passport?

The quick answer is: it depends. It depends which countries and what your nationality is.

For most of Europe, the Schengen Agreement is in force link

meaning that you can cross borders without showing credentials. But not all European countries are party to the agreement, and there a different rules if you are European versus, for example, Asian.

Taking the Eurostar from London to Paris last summer, I had to show a passport. On a bus from France to Spain several years ago, they did not make us show passports or I.D. at the border.

You have to show a passport to get in and out of the U.K. But not the rest of the EU. There has been talk on the news about the border controls being tightened because of the refugees but I don’t think that has happened

You don’t as long as you are within the schengen zone.

In many European countries they may still ask you when traveling by train, though.

Also in many Eueopean countries you need to carry a form of legal ID.

As stated before the Schengen Area is where you can travel across borders without the usual border controls. It was named after the town in Luxembourg where the agreement was signed. Luxembourg is good example of why this kind of agreement is necessary in modern Europe. I live in Luxembourg and it is a very small country bordered by Belgium, France and Germany. Every day more than 150,000 people commute from these three countries to Luxembourg to go to work, could you imagine the chaos and tail backs at motorway border controls, once in the morning and once in the evening, every day? It just would not work.

For certain modes of transport you still have to show ID, doesn’t have to be a passport though. For example you can fly from Luxembourg to Berlin and only need to show a drivers license.