Rûm (Template:IPA-al; singular Rûmi), also transliterated as Roum (in Koine Greek ?, Rhomaioi, meaning "Romans"; in Arabic ar-R?m; in Persian and Ottoman Turkish Rûm; in Turkish: Rum), is a generic term used at different times in the Muslim world to refer to:
The name derives from ?, Rhomaioi: "Romans". It refers to the Byzantine Empire, which was then simply known as the "Roman Empire" and had not yet acquired the designation "Byzantine", an academic term applied only after its dissolution. The city of Rome itself is known in modern Arabic as R?m? ? (in Classical Arabic R?miyah ). The Arabic term Rûm is found in the pre-Islamic Namara inscription and later in the Quran. In the Sassanian period (pre-Islamic Persia) the word Hr?m?y-?g (Middle Persian) meant "Roman" or "Byzantine", which was derived from Rhomaioi.
The Qur'an includes Surat Ar-Rum (the sura dealing with "the Romans", sometimes translated as "The Byzantines"). The people, known today as Byzantine Greeks, were inhabitants of the Roman Empire and called themselves or ? Rhomaioi, Romans. The term "Byzantine" is a modern designation to describe the Eastern Roman Empire, particularly after the major political restructuring of the seventh and eighth century. The Arabs, therefore, naturally called them "the Rûm", their territory "the land of the Rûm" and the Mediterranean "the Sea of the Rûm". They called Ancient Greece by the name "Y?n?n" (Ionia) and ancient Greeks "Y?n?n?m" (similar to Hebrew "Yavan" [?] for the country and "Yevanim"  for the people). Ancient Romans were called "R?m" or sometimes "Latin'yun" (Latins).
Al-R?m? is a nisbah designating people originating in the Byzantine Roman Empire or lands that formerly belonged to Byzantine Roman Empire, especially Anatolia. Historical people so designated include the following:
Later, because Muslim contact with the Byzantine Empire most often took place in Asia Minor (the heartland of the state from the seventh century onward), the term Rûm became fixed there geographically and remained even after the conquest by the Seljuk Turks so their territory was called the land of the Seljuks of Rûm or the Sultanate of Rûm. But as the Mediterranean was "the Sea of the Rûm", so all peoples on its north coast were called sweepingly "the Rûm".
After the conquest of Constantinople, Mehmed II declared himself Kayser-i Rum, literally "Caesar of the Romans". During the 16th century, the Portuguese used "rume" and "rumes" (plural) as a generic term to refer to the Mamluk-Ottoman forces they faced then in the Indian Ocean.
Under the Ottoman Empire's Millet system, Greeks were in the "Rum Millet" (Millet-i Rum). In today's Turkey, Rum are the Turkish citizens of Greek ethnicity. The term "Urums", also derived from the same origin, is still used in contemporary ethnography to denote Turkic-speaking Greek populations. "Rumeika" is a Greek dialect identified mainly with the Ottoman Greeks.
Chinese, during the Ming dynasty, referred to the Ottomans as Lumi (), derived from Rum or Rumi. The Chinese also referred to Rum as Wulumu during the Qing dynasty. The modern Chinese name for the city of Rome is Luoma ().
There are differing opinions among Islamic scholars regarding the identity of Rûm in the modern day. Various books have been written on the topic and the relevance of the identity of Rûm in Islamic eschatology caused much debate to take place regarding the issue.
Musa Cerantonio, in his book 'Which Nation does R?m in the Ad?th of the Last Days refer to?', suggests that the title of Rûm was passed from the Roman Empire based in Italy to the Byzantine Empire, then to the Ottoman Empire when the Ottomans defeated the Byzantines, and openly proclaimed to be the inheritors of Rome and its leader Mehmed II called himself the Caesar of Rome (Qaysar al-Rûm), and the title of Rûm was then passed to the successors of Rûm, the modern Republic of Turkey. The book argues that the definition of Rûm has never been defined by ethnicity, geography or religion but that Rûm was always understood to be a political term and that it was only by conquest and succession that a nation would become the inheritors of the title of Rûm.