Sophie is received into the Russian Orthodox Church and christened Ekaterina Alekseyevna on 28 June 1744.
On 28 June 1744, Sophie of Anhalt-Zerbst formally converted from Lutheranism to Russian Orthodoxy, a decisive step required of any foreign princess intending to marry into the Romanov dynasty. In an elaborate ceremony at the Russian court, she was received into the Orthodox faith and given the new name Ekaterina Alekseyevna — Catherine, daughter of Alexei — the name by which history would remember her.
This conversion was far more than a religious formality; it was a profound act of political and cultural assimilation. Sophie had spent months studying Russian language, customs, and Orthodox theology with remarkable diligence, reportedly rising at night to study by candlelight and even suffering a severe illness from her intense efforts, which nonetheless won her sympathy at court.
By embracing Orthodoxy so thoroughly and publicly, Catherine signaled her complete commitment to her adopted homeland, distinguishing herself from her husband Peter, who remained conspicuously attached to his Prussian and Lutheran sympathies even after his own conversion. Catherine's genuine effort to become Russian in language, faith, and manner won the loyalty of the Orthodox clergy and the Russian people — an asset that would prove invaluable eighteen years later when she needed broad support to seize the throne herself.