The history of the number zero stretches from early civilizations in the fertile crescent (now known as the Middle East) all the way into modern times. This means the question of who invented the number zero has no simple answer, since different civilizations expanded upon the concept over many thousands of years. The basic history of numbers, at least as far as the standard system used today, consists of numerals devised by many famous Arabian mathematicians; however, the first actual recorded use of the modern zero appeared on a carved stone in Cambodia hidden away from Khmer Rouge. Yes, the very first zero complete with rounded edges, as far as archeologists can tell, stems from the early Cambodian people.
Since zero represented a sum of nothing, it took ancient math many years to fully understand the idea of a zero sum needing representation. Yet many thinkers of the ancient world managed to conceive mathematical theories which relied upon numbers that one cannot physically see or count. Though the zero stands for nothing, the course of its development is anything but a history of nothingness.
The first recorded numbering systems appeared between 5000 and 4000 BCE in Sumeria, then located in Mesopotamia. In addition to developing a counting system, the Sumerians also developed the standard minute and hour, using sexigesimal (based on 60) counting. However, the Sumerian system never recognized zero as a number, and no set placeholders for numbers like 60, 605, or 10,500 have been agreed upon.
The Babylonians, another Mesopotamian civilization, inherited their numerical ideas from the Sumerians. However, the Babylonians took it one step further. Using a character that resembled two wedged lines placed perpendicular to each other, the Babylonian numerical system finally found a placeholder for the zeroes in numbers like 10, 605, and 10,500. Although they filled a numerical column that zero now occupies, the Babylonians never thought of zero as a number of its own.
Usually in the case of famous historical concepts, three cultures played some part in their development: the Chinese, the Greeks, and the Egyptians. However, none of these ancient cultures recognized zero as a number. The Chinese invented invented a bamboo system that only recognized the numbers one through nine. The Greeks picked up their mathematical system from the Egyptians, who also failed to recognize zero or use any sort of placeholder for numbers like 100.
While most of the early development of the number zero took place over in the Middle East, it also appeared independently in the Americas. Sometime around 350 CE, the Mayan people began using zero in their calendar system. However, some posit that pre-Mayan civilizations began using zero as a placeholder starting in 36 BCE, citing the fact that these people made calculations in the millions and would need a placeholder to make these calculations.