1. Mandarin Chinese: 939 million
2. Hindi: 615 million
3. English: 379 million
4. Spanish: 534 million
5. Arabic: 274 million
6. Bengali: 265 million
7. Russian: 154 million
8. Portuguese: 257 million
9. Indonesian: 198 million
10. Urdu: 170 million
Note: This list considers native speakers only. If we include second language speakers, English would likely rank higher.
It's important to note that these numbers can vary depending on the source and methodology used.