Sadajiro Tsuchida (土田 定次郎, Tsuchida Sadajirō,1908-1976) was a Japanese paleontologist and petroleum geologist. He was born in Gifu (岐阜) prefecture, Japan, moved to Ssupingkai (四平街, Shiheigai), Manchuria (満州, Mansyū) as a teacher of elementary school, and surveyed the periphery of the city. He moved back to Japan, majored in geology and paleontology at the Tohoku Imperial University (東北帝国大学, Tōhoku teikoku daigaku). After graduation, he moved to Pyongyang (平壌, Pyon-yan), Korea, as an assistant professor and a professor of the mining engineering course at the Taedong Technical college (大同工業専門学校, Daidō kōgyō senmon gakkō). He moved back to Japan again, joined the Teikoku Oil Company (帝国石油株式会社, Teikoku Sekiyu kabushiki-gaisya), Arabian Oil Company (アラビア石油株式会社, Arabia Sekiyu kabushiki-gaisya), and some associated companies, was engaged in oil exploration in some foreign countries. While the period, he gave lectures at Hokkaido University, Niigata University, and Saitama University. He became a professor of petroleum geology (燃料地質学, nenryō chisitsugaku) at Waseda University (早稲田大学, Waseda daigaku) and a researcher (Concurrent post) (兼任研究員) at Waseda Research Institute for Science and Engineering (早稲田大学 理工学研究所, Waseda daigaku rikōgaku kenkyūjo). He died in 1976.