Sun Tzu or Sun Zi was a Chinese mathematician, flourishing between the 3rd and the 5th century AD.
Interested in astronomy and trying to develop a calendar, he investigated Diophantine equations. He is only known for authoring Sun Tzu Suan Ching 孙子算经 (pinyin: Sun Zi Suan Jing; literally, "Sun Tzu's Calculation Classic"), which contains the Chinese remainder theorem.
English translation of Sun Zi suanjing: (The Mathematical Classic of Sun Zi)