Ertuğrul Gazi Tomb is the tomb of Ertuğrul Gazi, the father of Sultan Osman I who was the founder of the Ottoman Empire. The tomb is located in Söğüt in the Turkish province of Bilecik. The construction of the mausoleum dates back to the 13th century AD, and it was restored several times during the Ottoman period, the most important of which was in 1757 during the reign of Sultan Mustafa III.