Who was the first queen before Queen Victoria?

Victoria's predecessor was William IV, who reigned from 1830 - '37.

His predecessor was his older brother George IV, but George died without leaving a legitimate heir, so the throne passed to William.

None of them were Kings of England - that title ceased to exist when the crowns of England and Scotland were united in 1707.

Their title, at that date was "King of The United Kingdom of Great Britain and Ireland."