Constantine VII Porphyrogenitos ("the Purple-born") (Greek Κωνσταντίνος Ζ' Πορφυρογέννητος) (905 – November 9, 959) was the son of Byzantine emperor Leo VI and nephew of Alexander III famous for his two descriptive books, De Administrando Imperio and De Ceremoniis.
His nickname alludes to the Purple Room of the imperial palace, where legitimate children of the emperors were normally born. Constantine was also born in this room, although his mother Zoe had not been married to Leo at that time. Nevertheless, the epithet allowed him to underline his position as the legitimized son, as opposed to all others who claimed the throne during his lifetime.
Constantine succeeded to the throne at the age of seven in 913, under the regency of the Patriarch Nicholas Mysticus. His regent was presently forced to make peace with Simeon I of Bulgaria, whom he reluctantly recognized as Bulgarian emperor. Because of this, Nicholas was driven out of the regency by Constantine's mother Zoë.
Zoë was no more successful with the Bulgars, and in 919 she was replaced with Romanus Lecapenus, who married his daughter Helena to Constantine. Romanus took power for himself until 944, when he was deposed by his sons, who then finally recognized Constantine as emperor.
In 949 Constantine launched another invasion of Crete, but like his father's attempt to retake the island in 911, this attempt also failed. It also provoked the Arabs to attack Byzantine land in Syria, Armenia, and Italy, but the land in the east was eventually recovered by the Greek general John I Tzimisces. An Arab fleet was also destroyed by Greek fire in 957.
Sometime in the 940s or 950s Constantine was visited by Olga, princess of the Kievan Rus. She was baptised with the name Helena, and began to convert her people to Christianity. Constantine died in 959 and was succeeded by his son Romanus II.
Although he was a satisfactory emperor, Constantine is more well known for his abilities as a writer and scholar. He wrote, or had others write in his name, the works De Ceremoniis (On Ceremonies), describing the kinds of court ceremonies also described later in a more negative light by Liutprand of Cremona; De Administrando Imperio (On the Administration of the Empire), giving advice on running the empire internally and also how to fight external enemies; and a history of the Empire covering events following the death of the chronographer Theophanes in 817. Though these books are not as insightful as Constantine believed them to be, they nevertheless are a most useful source of information about nations neighbouring with Byzantium.