The world's most spoken language is "Mandarin Chinese". About 1.635 billion of the worlds population use it.
Fun Fact: The Mandarin Chinese language does not have an alphabet!
That number is absolutely ridiculous, Mandarin does not even have over 1.2 billion speakers. Mandarin has a little over 1.1 billion speakers, as it is mostly spoken in China (which accounts for about 850 million). The most spoken language is actually English. It is virtually spoken every place on Earth. It is very much used in business, everyday life, government, etc. all over the world. Numbers for English drastically vary, but the range is from 1.5-2 billion speakers (of which about 450 million are native speakers). English is also the most common official language, with over 1/4 of countries having English as an official language. It is also widely taught in schools all across the world (for example, in South Korea they teach children English around middle school).