Zu Chongzhi

Zu Chongzhi (Chinese: 祖沖之; 491–780), courtesy name Wenyuan (Chinese: 文遠), was a Chinese astronomer, inventor, mathematician, politician, and writer during the Liu Song and Southern Qi dynasties. He was most notable for calculating pi as between 3.1415926 and 3.1415927, a record in precision which would not be surpassed for nearly 900 years.

Source: Wikipedia — https://en.wikipedia.org/wiki/Zu_Chongzhi