Kassia, Cassia or Kassiani (Greek: Κασσιανή, romanized: Kassianí, pronounced [kasia'ni]; c. 810 – before 865) was a Byzantine-Greek composer, hymnographer and poet.

Smitten by Kassia's beauty, the young emperor approached her and said: "Through a woman [came forth] the baser [things]," referring to the sin and suffering coming as a result of Eve's transgression.

Kassia promptly responded, "And through a woman [came forth] the better [things]," referring to the hope of salvation resulting from the Incarnation of Christ through the Virgin Mary.

Medieval Greek: [c(e) ek ʝyneˈkos ta ˈkrito]Unsatisfied with her response, Theophilos rejected her and chose Theodora as his wife.

[8] Although many scholars [weasel words] attribute this to bitterness at having failed to marry Theophilos and to become empress, a letter from Theodore the Studite indicates that she had other motivations for wanting a monastic life.

It had a close relationship with the nearby monastery of Stoudios, which was to play a central role in re-editing the Byzantine liturgical books in the 9th and 10th centuries, thus ensuring the survival of her work (Kurt Sherry, p. 56).

[9] Emperor Theophilos was a fierce iconoclast, and any residual feelings he may have had for Kassia did not preserve her from the imperial policy of persecution for her defence of the veneration of icons.

"[9] After the death of Theophilos in 842 his young son Michael III became Eastern Roman Emperor, with Empress Theodora acting as Regent.

[1] The most famous of her compositions is the eponymous Hymn of Kassia (also known as the Troparion of Kassiani), which is chanted each year for Great and Holy Wednesday as a doxastichon occurring at the end of the aposticha of orthros and the lamp-lighting psalms of the Presanctified Liturgy.

Theophilus, overcome with sadness, cried and regretted that moment of pride when he rejected such a beautiful and intellectual woman; then he noticed the papers on the table and read them.

[13] The music for the hymn is slow, sorrowful and plaintive, lasting about ten to twenty minutes, depending on tempo and style of execution.

"The terrible race of the Armenians is deceitful and extremely vile, fanatical, deranged, and malignant, puffed up with hot air and full of slyness.

[1] These literary genres were chiefly dominated by men, so her contributions would have been unusual; Byzantinist Andrew Mellas noted that "perhaps this was an advantage for Kassia and accounts for her originality".

[19] Her epigrams are particularly reminiscent of similar works by her colleague Theodore the Studite, and are characterized by a concise and straight forward presentation,[17] often including witty or humorous elements.

Contemporary historians such as Glykas, Ptochoprodromos, Kodinos, Zonaras, and Georgios Amartolos described her exile in Italy during the Iconoclasy wars and later settled and died in Kasos sometime between 867 and 890.

In August 2019, English singer-songwriter Frank Turner included a song told from her point of view on his album No Man's Land.