Muslim population growth is the population growth of Muslims worldwide. Between 2015 and 2060, Muslim population is projected to increase by 70%. This compares with the 32% growth of world population during the same period. The young median age and high fertility rate of Muslims relative to other religious groups are significant factors behind Islam's population growth. As of 2015, Muslims have the highest fertility rate of any religious group – an average of 2.9 children per woman, well above replacement level (2.1) —well above the global rate—but down from 4.3 in 1990–1995.

According to a study published in 2011 by Pew Research, whilst there is a lack of reliable data, religious conversion might have no net impact on the Muslim population as the number of people who convert to Islam is thought to be similar to those who leave Islam. According to another study published in 2015 by the Pew Research Center, Islam is expected to gain a net of 3 million adherents through religious conversion between 2010 and 2050, which makes Islam the second largest religion in terms of net gains through religious conversion after religiously unaffiliated, mostly comes from Sub-Saharan Africa (2.9 million).