Tatsuo Nitta, whose name in Japanese is written as 新田たつお, is a Japanese manga artist recognized for creating the long-running and commercially successful series Shizukanaru Don – Yakuza Side Story, also known as The Quiet Don. Nitta was born on October 25, 1953, in Osaka Prefecture, Japan. After graduating from university, he worked as a junior high school art teacher before pursuing a career in manga. He made his debut in 1975 with the work Daidokoro no Oni (台所の鬼), which was published in Kodansha's Weekly Shōnen Magazine.

Throughout the 1980s, Nitta created several manga series that were well-received. Among these were Big Magnum Kuroiwa Sensei (ビッグマグナム黒岩先生), which was adapted into a live-action film in 1985, and Kochira Bonjin-gumi (こちら凡人組). However, his most significant commercial and critical success began in 1988 with the launch of Shizukanaru Don – Yakuza Side Story. The series started serialization in Jitsugyo no Nihon Sha's seinen manga magazine Weekly Manga Sunday on November 15, 1988, and ran for over 24 years until its conclusion on January 8, 2013. The series was compiled into 108 tankōbon volumes, with the final volume released on June 29, 2013, and it has sold over 45 million copies in Japan. In 2013, Shizukanaru Don was awarded the Grand Prize at the 42nd Japan Cartoonists Association Award, with judges citing its absurdity and fun as key factors in its significance.

Shizukanaru Don has seen numerous adaptations across different media, forming a central part of Nitta's career as an original creator. The story, about a yakuza boss who leads a double life as a designer at a lingerie company, was first adapted into an original video animation by Tokyo Movie Shinsha, released on April 12, 1991. This was followed by a Japanese television drama series in 1994, live-action films in 2000 and 2009, a drama CD in 2010, and a new four-part live-action film project announced in 2023. Beyond this flagship work, Nitta has continued to create manga, with titles such as Chen Jie (チェン爺) in 2000 and Taimu Surippu (隊務スリップ) in 2013, demonstrating a consistent and ongoing career as a writer and illustrator.