The top three are English, Spanish and Mandarin Chinese, but the order depends on what you mean by "speakers". If you count the inhabitants of countries by official language, then it must be English, principally because India has a population comparable to China and one official language in India is English. Would you consider "speakers" as people with the language as their mother tongue? Again English wins out here, because a lot of people in China and the Spanish world speak local languages such as Kirguizi or Quechwa in their families. In Spain itself for instance 3 million alone have Catalan as their mother language, not Spanish. In countries like the US, GB or Australia the local languages are much more infrequent. This is a pity IMHO, I like linguistic diversity. And if you think "speakers" are people who can speak the language ok but it's not mother tongue, then clearly it's English again. A customer in Denmark phones a supplier in France, what language do they normally speak in? This is the strength of English worldwide, it's the language of business, culture, internet etc. for people who speak it as a second language. So whichever way you look at it, I'd put my money on English having the most speakers.