There is no doubt about it: if you want to travel the world and be understood in as may places as possible, the best language you could possibly learn is English. 
English is the primary language across vast swaths of land, including much of North America, parts of Europe, and Australia, to name only a few. But it is also studied and spoken widely as a second language in a number of places as well. In fact, you will find that many people know at least conversational English — more than enough to get by.

But seeing as this is being written in English, it’s probably safe to assume you’re at least mostly fluent in English already. So what are some other useful languages for world travel?

Depending on where you are interested in traveling — and ignoring for the moment how difficult a language may or may not be to learn — here are the languages that will get you the farthest: Spanish, Mandarin, Russian, and Arabic.

Spanish
Although dialects of Spanish will vary from region to region, Spanish is a language that will allow you to communicate with people all over the globe, from Spain to Mexico to South America and beyond. Additionally, Spanish will allow you to grasp enough written Portuguese to get by in other regions as well.

Mandarin
This Chinese dialect is the language spoken by the largest number of people in the world. It is very useful throughout eastern Asia and other places as well. This is beneficial in business and tourism. 

Russian
Russian is useful only because people in the former USSR never learned to speak English. It’s not like most other parts of the world, where English is the common second language: In Russia the second language isn’t English.

Arabic
Arabic will take you far throughout the Middle East. Even in places where it isn’t the first language, it is a second language for people in the Islamic region.

Other useful languages include French, Hindi, and German, which will take you far depending on the region in which you are most interested in traveling. Regardless of where you go, you will surprise yourself by how much of the local dialect you pick up — and how quickly!