1. Mandarin Chinese: Spoken by over 1 billion people, primarily in China.
2. Hindi: Spoken by over 600 million people, primarily in India.
3. English: Spoken by over 370 million people as a first language, but with over 1.5 billion speakers overall (including second language speakers).
These numbers are based on estimates and can fluctuate depending on the source. However, it's clear that Mandarin Chinese, Hindi, and English are the most widely spoken first languages globally.