In the case of an emergency, 911 is the number you call in the United States. On the other end of the line is an operator who will work to understand the situation and, in the best-case scenario, send the first responders needed. In other countries, there are similar emergency systems, but the number to dial may vary.
The emergency lines in the twenty most visited countries in the world
There are a few countries that do use 911 as their emergency line:
The numbers can be found in this PDF published by the US State Department, but we have provided the numbers for the 20 most visited countries worldwide.
The response time may vary between countries, but many countries have built up their emergency response systems and are considered reliable for locals and tourists alike. It is recommended to save the emergency number on your cellphone or keep it close at hand while traveling, as you never know when you may need to make an emergency call.