The foundation and rise of the Ottoman Empire (1299 – May 29, 1453) is the period that starts with the weakening of the Seljuk Sultanate of Rûm in the very early fourteenth century and ends with the fall of Constantinople on May 29, 1453.The rise of the Ottomans correlates with the decline of the East Roman (Byzantine) Empire, which generates the shift in power from a singular Christian European society to an Islamic influence.

The beginning of this period is characterized by the Byzantine-Ottoman Wars, which last for a century and a half.

During this period, the Ottoman Empire gains control of both Anatolia and the Balkans.Immediately after the establishment of the Anatolian beyliks, some Turkic principalities unite with the Ottomans against the Empire.

This period also witnesses the Sultanate of Rûm's defeat by the Mongols in the fourteenth century and is followed by the Growth of the Ottoman Empire — a period referred to as Pax Ottomana, the economic and social stability attained in the conquered provinces of the Ottoman Empire, by some historians.