It's important to note that there are different ways to measure "most common," and depending on how you define it, the answer might vary.
* Number of native speakers: Mandarin Chinese has the most native speakers, with around 939 million people worldwide.
* Total number of speakers: Including non-native speakers, Mandarin Chinese still holds the lead, though the numbers are harder to pin down precisely.
However, English is often considered the most widely spoken language due to its global use in business, education, and media.