Who invented zero?

Nobody invented zero in a single flash. It crept into mathematics in two stages. First came zero as a placeholder: a mark that says "nothing in this column", so that 205 is not confused with 25. Babylonian scribes had a base-60 positional system by the middle of the 2nd millennium BC but at first marked an empty position only with a space between numerals. The placeholder sign they adopted by 300 BC was never used alone and was not treated as a numerical value. Across the ocean, the Mesoamerican Long Count calendar needed zero as a placeholder, and its earliest known date, from 36 BC, is on a stone at Chiapa de Corzo.

The second stage was zero as a number you can calculate with. That step is credited to India. A Jain cosmology text dated internally to AD 458 already used decimal place value with a zero, and in the 7th century Brahmagupta wrote down rules for it. His Brahmasphutasiddhanta is the earliest known text to treat zero as a number in its own right, not just a placeholder. He got zero plus zero right, but he described division by zero incorrectly, a problem we still handle by calling it undefined.

Greek thinkers, for their part, were unsure zero was a number at all, and some asked, "How can not being be?" Meanwhile the idea travelled. The word zero comes from Arabic sifr, which began as a word for empty. About 825 al-Khwarizmi explained the use of zero in a book, and the Latinization of his name is where the word algorithm started. Fibonacci, credited with introducing the decimal system to Europe, wrote that with nine figures and the sign 0 any number may be written, though only in the 16th century did these numerals become the predominant ones in Europe.

So the true answer to "who invented zero?" is that Babylonian scribes, Mesoamerican calendar-makers and Indian mathematicians all found parts of it, and India turned it into a number.