Islam spread in Ethiopia along the trade routes connecting ports on the Gulf of Aden with central Ethiopia. In August 2023, archaeologist Hitoshi Endo (ILCAA) and cultural anthropologist Chikage Oba (Arsi University, Ethiopia) discovered a historical site in Sakate, West Hararghe Zone, Oromia Region, southeastern Ethiopia, centered around a mosque, one of the largest in sub-Saharan Africa before the 19th century. The site is located far from the aforementioned trade routes and has not been subject to academic research to date. Endo and Oba re-examined Islamic historical sites in southeastern Ethiopia from September to October 2025. At this presentation, historian Hiroki Ishikawa (ILCAA) will first provide an overview of the Islamic history of southeastern Ethiopia. Next, Endo will explain the results of the re-investigation of the Sakate site and report on the remains of several mosques discovered during archaeological surveys in the Shebelle River basin.