The birth of Islam over fourteen centuries ago was a monumental event in human history with an everlasting effect on humanity. For centuries, researchers have contemplated on the growth and distribution of Muslims throughout the world. This book presents a reliable estimate of the world Muslim population since the inception of Islam at the start of the seventh century to the end of the twenty-first century. In this book, the world is divided into five continents, each of which is further divided into non-overlapping regions, and these in turn are divided into current countries. A centennial data estimate for each region and current country from 600 AD to 2100 AD (approximately 1 H to 1500 H) of the total population, and the corresponding Muslim population and its percentage are provided. Furthermore, the same data in decennial order from 1790 to 2100 (or 1210 H to 1520 H) is provided for each region and country. These data are summarized to be a reference for other studies and discussions related to the Muslim population. The presented data show that the percentage of world Muslim population with respect to the total world population has increased steadily from 3% in 700 AD or 100 H to 7% in 800 AD or 200 H, to 11% in 900 AD or 300 H, to 13% in 1000 AD or 400 H, reaching 16% in 1700 AD or 1100 H. But it dropped to 13% in 1800 AD or 1200 H, to increase to 14% in 1900 AD or 1300 H. This percentage has been increasing by one percentage point per decade since 1950 AD or 1370 H, reaching 25% in 2020 AD or 1440 H. The rate of increase of the world Muslim population is expected to slow down, increasing their percentage to 30% by 2050 AD or 1470 H and 35% by 2100 AD or 1520 H.