Sun Tzu (Chinese: 孫子; Pinyin: Sūn Zǐ) ("Master Sun") is an honorific title bestowed upon Sūn Wǔ (孫武; c. 544 BC – 496 BC), the author of The Art of War, an immensely influential ancient Chinese book on military strategy. He is also one of the earliest realists in international relations theory.
In the author's name, Sūn Wǔ, the character wu, meaning "military", is the same as the character in wu shu, or martial art. Sun Wu also has a courtesy name, Chang Qing (長卿; Cháng Qīng).