Peter III dies at Ropsha, at the hands of Alexei Orlov (younger brother to Grigory Orlov, a court favourite and a participant in the coup) on July 17, 1762—eight days after the coup and just six months after his accession to the throne.

Historians find no evidence for Catherine's complicity in the supposed assassination.

At the time of Peter III's overthrow, other potential rival claimants to the throne exist: Ivan VI (1740–1764), in close confinement at Schlüsselburg, in Lake Ladoga, from the age of six months; and Yelizaveta Alekseyevna Tarakanova (1753–1775).

Ivan VI will be assassinated during an attempt to free him as part of a failed coup against Catherine: Catherine, like Empress Elizabeth before her, gives strict instructions that he is to be killed in the event of any such attempt.

Ivan will be thought to be insane because of his years of solitary confinement, so might have made a poor emperor, even as a figurehead.

Catherine, though not descended from any previous Russian emperor of the Romanov Dynasty (she descends from the Rurik Dynasty, which preceded the Romanovs), succeeds her husband as empress regnant.

She follows the precedent established when Catherine I (born in the lower classes in the Swedish East Baltic territories) succeeded her husband Peter the Great in 1725.

Historians debate Catherine's technical status, some seeing her as a regent or as a usurper, tolerable only during the minority of her son, Grand Duke Paul.

In the 1770s, a group of nobles connected with Paul (Nikita Panin and others) will consider a new coup to depose Catherine and transfer the crown to Paul, whose power they envisage restricting in a kind of constitutional monarchy.

However, nothing will come of this, and Catherine will reign until her death.