Boris 1 was also called Michael, he was a Bulgar whose absence at Thessalonike supposedly gave an opportunity to the exiled "Macedonians" in Bulgaria (Byzantines from Adrianople carried away into captivity by Krum 1 in 813 and living under the Bulgars north of the Danube) to begin crossing the Danube with their goods to return to the empire: Leo Gramm. 232, Georg. Mon. Cont. 818. The date was 836/838; see Basilios 7. He was evidently a Bulgar leader. He is probably to be identified with Boris I, ruler of the Bulgars from 852 to 889, who adopted the name Michael on becoming a Christian. The reference here is probably anachronistic; the chronicle tradition from Symeon the Logothete names three Bulgar leaders in this passage as Michael, Baldimer and Symeon, the names of rulers of the Bulgars later in the ninth century which have wrongly been inserted here. See also Vladimir 1.

Called Bogaris or Bogoris: Ps.-Symeon 664 (Bogaris), 665 (Gobori), Theoph. Cont. IV 13 (p.162) (Bogoris). Ruler of Bulgaria (ὁ ἀρχων Βουλγαριας); he allegedly planned to attack the Empire while Theodora 2 was at the head of the government but was deterred by the consideration that if he were defeated it would be at the hands of a woman: Ps.-Symeon 664, Theoph. Cont. IV 13 (p. 162), Zon. XVI 2.1-3 (unnamed ὁ δὲ τῶν Βουλγάρων ἄρχων), Genesius IV 7 (unnamed ὁ ἀρχηγὸς Βουλγαρίας). Boris 1 had a sister (Anonyma 7) who was living in captivity in Constantinople; she had become a Christian and after she was allowed to return (cf. Theodoros 76) she tried to convert Boris 1: Ps.-Symeon 664, Theoph. Cont. IV 14 (pp. 162-163), Zon. XVI 2. 4-7 (ἀδελφὴ δὲ τοῦ ἄρχοντος Βουλγαρίας).

Ruler of Bulgaria (ἄρχων Βουλγαρίας); Boris 1 was attacked by the Romans under Michael III (Michael 11) and the kaisar Bardas 5 at a time when the Bulgars were suffering from famine and could not resist; they asked for peace, offering to accept Christianity and submit to the Romans; the Romans agreed and Boris 1 was baptised by the emperor and received the baptismal name of Michael; the Bulgar notables also received baptism: Leo Gramm. 238, Georg. Mon. Cont. 824, Ps.-Symeon 665, Theoph. Cont. IV 14 (pp. 162-163). The date was 863/864 (see below). On his return home he supposedly had the Last Judgement represented on his palace walls by the painter Methodios 2; this provoked a rising among his people which he suppressed, afterwards converting them all to Christianity; he then negotiated changes to his frontiers with the Romans, which were moved south from Sidera to Debelton; the new area was called Zagoria: Ps.-Symeon 665-666, Theoph. Cont. IV 15 (pp. 163-165) (where the painting is said to have been on the walls of a hunting lodge; he asked Methodios 2 to paint any subject he liked provided that it would terrify the viewer), cf. Zon. XVI 2. 8-16 (the plague, his conversion, the revolt and the new frontiers).

Ruler of the Boulgaroi (ὁ καθηγεμὼν Βουλγάρων); after the Roman victory over the Arabs at Porson (Poson) Boris 1 sought to make peace; his people were suffering from famine and he agreed to become a Christian with his people, and accepted the name Michael, from that of the emperor: Genesius IV 16. On these events, to be dated 863/864, cf. Browning, Byzantium and Bulgaria, pp. 145-147, and, for the date of the baptism, see A. Vaillant and M. Lascaris, "La date de la conversion des Bulgares", Revue des Etudes Slaves, 13 (1933), pp. 5ff. See also Obolensky, The Byzantine Commonwealth. According to the Liber Pontificalis, the Bulgar king Michael sent envoys to the bishop of Rome, Nicolas (Nikolaos 28), delivering gifts and seeking help with the conversion of his people; the envoys arrived in August 866; Nikolaos 28 sent the bishops of Populonia and Portus, Paulus and Formosus (Paulos 57 and Formosus 1) to preach to the Bulgars; Michael (Boris 1) gave them a warm welcome and expelled from Bulgar territory all missionaries of other nationality; he further asked for more priests to be sent and also requested that Formosus be appointed archbishop in Bulgaria: Lib. Pont. 107. 68-75.

Boris 1 is attested as ruler (archon) on an inscription dated 5 October 870 (year of the world 6379, indiction 4, October 5) (ἐπὶ Μιχαὴλ τ[οῦ εὐκλ] - έους κ<ὲ> φιλ[ο]χρ[ίστου] - ἄρχων[τοσ]): Beshevliev, Spätgr. u. spätlat. Inschr., nr. 51 (= E. Kalinka, Antike Denkmäler, p. 289, nr. 367; Grégoire, Byz. 45 (1939), pp. 227- 234 and 693ff.; V. Beshevliev, Die protobulgarischen Inschriften (Berlin, 1963), pp. 327ff., nr. 87) at Cherven (district of Ruse in Bulgaria).

In c. 865 Boris 1 was the addressee of a long letter from the patriarch Photius (Photios 1) on theological matters: Photius, Ep. 1 (addressed τῷ περιφανεστάτῳ καὶ περιβλέπτῳ ἠγαπημένῳ ἐν κυρίῳ πνευματικῷ υἱῷ Μιχαὴλ τῷ ἐκ Θεοῦ ἄρχοντι Βουλγαρίας).

Michael also called Boris 1 (Μιχαὴλ ὁ Βορ́σης) was ruler of Bulgaria; he made war, unsuccessfully, on the Croats and finally made peace: Const. Porph., DAI 31, 62ff.

Michael (Boris 1) was the son of Presiam 1; he waged war on the three rulers of Serbia, Mountimeros 1, Stroimeros 1 and Goinikos 1, to avenge the death of his father: Const. Porph., DAI 32, 42. Father of Bladimeros (Vladimir 1); when he was defeated and his son taken prisoner he sued for peace; his son was returned safely and he exchanged gifts with Mountimeros 1: Const. Porph., DAI 32, 47. He married a Bulgarian lady to Klonimer (PBE II; the son of the Serb Stroimeros 1): Const. Porph., DAI 32, 64.

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