Isaac I Komnenos or Comnenus (Ancient Greek: Ἰσαάκιος Κομνη­νός, Isaakios Komnēnos; c. 1007 – 1 June 1060) was Byzantine emperor from 1057 to 1059, the first reigning member of the Komnenian dynasty.

As emperor, he rewarded his supporters, but also embarked on a series of fiscal measures designed to shore up revenue and eliminate the excesses allowed to flourish under his predecessors.

Shortly after, Isaac fell ill, and on the advice and pressure of Michael Psellos, he abdicated his throne in favour of Constantine X Doukas, retiring to the Stoudion monastery where he died later in 1060.

Isaac was the son of Manuel Erotikos Komnenos, who reportedly served as strategos autokrator of the East under Emperor Basil II and defended Nicaea against the rebel Bardas Skleros in 978.

According to Nikephoros Bryennios the Younger, the two children were raised with the utmost solicitude and the best tutors at the Stoudion monastery, with care taken to teach them military exercises and hunting.

[7] At a young age, perhaps as early as 1025, Isaac married Catherine of Bulgaria (born c. 1010), a daughter of Ivan Vladislav (r. 1015–1018), the last Tsar of the First Bulgarian Empire.

[5][8] From c. 1042 he held the post of stratopedarches of the East—likely denoting that he was domestikos ton scholon, commander-in-chief, of the eastern field army, but this title is not explicitly attested[9]—and the ranks of magistros and vestes.

[13] This exacerbated the already simmering dislike of the military aristocracy for the "regime of eunuchs and civilian politicians" that had dominated the empire during the last decades of the Macedonian dynasty.

[15][16] As the historian Anthony Kaldellis comments, this was a formidable assemblage, as the families represented in it, all of them descended from military men promoted by the warrior-emperor Basil II, would define "the future of the empire for the next thirty years, indeed for the next century and more".

John Skylitzes, who wrote later in the century, reports that the emperor treated the generals courteously, but agrees that he refused outright to consider the honours they claimed for themselves, notably the promotion of Isaac and Kekaumenos to the rank of proedros.

A second delegation to the chief minister, the protosynkellos Leo Paraspondylos, was received in similar manner, and according to Psellos Isaac could barely restrain his colleagues from attacking the emperor then and there, in his own throne room.

[17][18] The conspirators contacted the veteran general Nikephoros Bryennios, who had unsuccessfully tried to usurp the throne from Theodora[19] but had recently been recalled by Michael VI as commander of the Macedonian army, and he apparently agreed to support them.

[21] It is unclear whether any of the rebels held command of troops; rather, according to Kaldellis, "they had to canvass for support among the officers and soldiers and forge orders of imperial appointment for themselves".

Michael offered to adopt Isaac as his son and to grant him the title of Caesar, making him effectively his successor, but this was rejected in a public audience.

[30] Back in Constantinople, however, a crowd of officials assembled in the Hagia Sophia and began protesting that by making a deal, the Emperor was forcing them to renounce their oaths to oppose the rebels.

[31][32][33] On the next day, 31 August, Isaac and his entourage crossed the Bosporus into Constantinople and entered the palace; on 1 September, he was crowned emperor by the Patriarch in the Hagia Sophia.

[38] The task he faced was truly herculean, as the politically weak emperors of the previous thirty years had fostered corruption and inefficiency, handing out titles and their attendant state salaries (rogai) in exchange for support.

[37] To fund his cherished army, Isaac was therefore obliged to begin strict economies: he reduced or abolished the rogai of those who had been awarded titles, enforced a stricter and more efficient collection of taxes, reclaimed misappropriated imperial estates, and cancelled grants of such lands and tax exemptions made under Constantine IX and Michael VI, particularly those that had been granted to monasteries and churches, using a law of Nikephoros II Phokas.

[45][46] He is also alleged to have worn imperial purple boots, a privilege restricted to the emperor, and which may indicate, according to Kaldellis, that Keroularios was influenced by Papal theories and conceived of the secular and clerical powers as co-equal, a traditional Byzantine approach known as a symphonia.

The contemporary Armenian historian Aristakes Lastivertsi reports that the Georgian lord Ivane took advantage of this opportunity to capture two Byzantine frontier forts as well as an imperial tax collector, and lay siege to Theodosiopolis.

[47] Constantine IX had famously abolished the military obligations of the Armenian thematic troops in exchange for cash payments, a step widely regarded, both by contemporaries and modern historians, as having catastrophic consequences for Byzantium's eastern defences, especially against the mounting Turkish threat.

[48] While Isaac does not appear to have acted to restore the thematic armies,[38] according to Kaldellis, the reaction of the local forces to these events does not appear to indicate a degradation of Byzantium's defensive abilities in the East, but rather the continued and successful application of old-established counter-raiding principles as codified in Nikephoros Phokas' De velitatione bellica a century earlier.

[50] Despite these events, Psellos claims that at this point Isaac's character changed markedly, and that he became "more haughty to such an extent that he held everyone else in contempt", including his own brother.

[52] On a hunt he fell ill. As the fever lasted for several days, Isaac, fearing he would die soon, named Constantine Doukas as his successor on 22 November 1059,[b] and agreed to resign and retire to a monastery.