Catherine of Bulgaria (Church Slavonic: Єкатерїна, Greek: Αἰκατερίνη, romanized: Aikaterini, Bulgarian: Екатерина, romanized: Ekaterina; died after 1059) was empress consort to Byzantine emperor Isaac I Komnenos and co-regent of Constantine X for a period after the abdication of her spouse in 1059.
She was a daughter of Ivan Vladislav of Bulgaria and his wife Maria, and thus a sister of Presian and Alusian.
Catherine was a daughter of Ivan Vladislav (reigned 1015–18), the last Tsar of Bulgaria.
He retired to the Stoudios Monastery and spent the remainder of his life, until his death in late 1060 or 1061, as a monk.
[2][4] Following her husband's abdication, she appears to have co-reigned for a while with Constantine X, but eventually she too retired to the Myrelaion monastery under the monastic name of Xene.