The Sword of Osman (; ) was an important sword of state used during the coronation ceremony of the sultans of the Ottoman Empire. The sword was named after Osman I, founder of the Ottoman Dynasty. The practice started when Osman I was girt with the sword of Islam by his mentor and father-in-law Sheikh Edebali. The girding of the sword of Osman was a vital ceremony which took place within two weeks of a sultan's accession to the throne. It was held at the tomb complex at Eyüp, on the Golden Horn waterway in the capital Constantinople. Even though the journey from Topkapi Palace (where the sultan resided) to the Golden Horn was short, the sultan would board a boat amid much pomp to go there. The Eyüp tomb complex was built by Mehmed II in honour of Abu Ayyub al-Ansari, a companion of Muhammad who had died during the first Muslim siege of Constantinople in the 7th century. The sword girding thus occurred on what was regarded as sacred grounds, and linked the newly enthroned sultan both to his 13th-century ancestors and to Muhammad himself.