Eudokia Makrembolitissa

Eudokia Makrembolitissa (Greek: Εὐδοκία Μακρεμβολίτισσα, romanized: Evdokía Makremvolítissa) was a Byzantine empress by her successive marriages to Constantine X Doukas and Romanos IV Diogenes. She acted as ruler with her two sons in 1067, and resigned her rule by marriage to Romanos IV Diogenes. When he was deposed in 1071 she resumed the rule with her son Michael VII, but was soon forced to resign again.

Because she essentially ruled in her own right during her rules and retained the title of empress, several modern scholars consider Eudokia to have been empress regnant in 1067 and 1071.

Source: Wikipedia — https://en.wikipedia.org/wiki/Eudokia_Makrembolitissa