Constantine VII Porphyrogennetos or Porphyrogenitus, "the Purple-born" (that is, born in the purple marble slab-paneled imperial bed chambers; Greek: Κωνσταντῖνος Ζ΄ Πορφυρογέννητος), was the fourth Emperor of the Macedonian dynasty of the Byzantine Empire, reigning from 913 to 959. He was the son of the emperor Leo VI and his fourth wife, Zoe Karbonopsina, and the nephew of his predecessor, the emperor Alexander.
Most of his reign was dominated by co-regents: from 913 until 919 he was under the regency of his mother, while from 920 until 945 he shared the throne with Romanos Lekapenos, whose daughter Helena he married, and his sons. Constantine VII is best known for his four books, De Administrando Imperio (bearing in Greek the heading Πρὸς τὸν ἴδιον υἱόν Ῥωμανόν), De Ceremoniis (Περὶ τῆς Βασιλείου Τάξεως), De Thematibus (Περὶ θεμάτων Άνατολῆς καὶ Δύσεως), and Vita Basilii (Βίος Βασιλείου).
His nickname alludes to the Purple Room of the imperial palace, decorated with porphyry, where legitimate children of reigning 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. Sons born to a reigning Emperor held precedence in the Eastern Roman line of succession over elder sons not born "in the purple".