Mandarin is the language spoken by the highest number of people
Much has been said about how English is becoming a bridge language for people from different cultures to communicate with each other. That said, the languages spoken in the most densely populated countries will always have a higher number of speakers.
This is the case with Mandarin, the most spoken language in the world. China, its birthplace, is one of the highest populated countries, which means that about 950 million people are native speakers. A further 200 million use it as a second language.