June 3, 2025 — A major new study by the Pew Research Center has confirmed that Islam is the fastest-growing religion in the world, expanding more rapidly between 2010 and 2020 than all other religions combined. The growth, according to the Global Religious Landscape report released on Monday, is primarily driven by demographics — not conversions.

“Muslims have more children and are younger, on average, than members of any other major religion,” the report notes.

Between 2015 and 2020, Muslim women had an average of 2.9 children, compared to 2.2 for non-Muslim women. Islam grew by nearly 350 million people in a decade, nearly three times the growth of Christianity and significantly outpacing all other faiths combined.

Key Findings:

• Islam now has around 2 billion adherents, making up about a quarter of the global population.

• While Christianity remains the largest religion with 2.3 billion followers, its global share is declining.

• For every one person who converted to Christianity, three left the faith between 2010 and 2020.

• Conversely, Islam was the only major religion where more people joined than left.

The study also highlighted a major demographic shift in religious affiliation globally:

• The religiously unaffiliated — those identifying as atheist, agnostic, or “nothing in particular” — grew by 270 million, with the most significant increase seen in the United States (a staggering 97% increase) and China, where 1.3 billion people are not affiliated with any religion.

• Hinduism, the world’s third-largest religion, grew by 126 million people, but its global share stayed the same.

• Buddhism was the only major religion to decline, losing 18.6 million followers, dropping from 5% to 4% of the world’s population.

Regionally, Islam experienced the most growth in Kazakhstan, Benin, and Lebanon, while its share declined in Oman and Tanzania. Meanwhile, Christianity declined by 1.8% globally, and by at least five percent in 40 countries.

“Islam’s growth,” the report emphasized, “has little to do with conversions — it’s a story of births, youth, and resilience.”

As the world’s religious landscape continues to shift, Pew’s data points to a future in which Islam’s demographic momentum will continue to reshape global faith dynamics for decades to come.