The accessions of the Tudors of England (Mary I and Elizabeth I) also counts as an example of consecutive queens regnant. It might have happened later on in the House of Stuart after the death in 1694 of Mary II, but for the fact that her widowed husband (King William III, House of Orange) was allowed to remain on the throne. Aside from his marriage to the elder daughter of King James VII/II, he was also a first cousin who ranked directly behind the Stuart sisters (Anne being the younger), he had helped depose his father-in-law during the Glorious Revolution, he had been enthroned as a joint sovereign with his wife, and he was already crowned. So Anne did not immediately succeed her childless older sister; but she nevertheless was heiress apparent to the British throne during the remaining years of her brother-in-law's life and reign (any hypothetical children William fathered, in the event that he remarried, were to follow his sister-in-law in the succession).
That being said, Queen Anne later on could herself have been succeeded by a queen regnant, had the Electress Sophia of Hanover survived her -- which almost happened. As it was, the latter was heiress presumptive to her kinswoman from the time of her accession in 1702 to her own dying day in 1714.
18th century Russia has been called the "Century of women", because of the number of females who ruled the country during that period. However, the country never had consecutive empresses regnant.
Bearing all this in mind, I was wondering if there have been additional examples in royal history of consecutive queens regnant -- or situations nearing that.