The 28-year-old from Leeds secured a unanimous victory in Sofia to become European champion in her first appearance at a major championship.
Gale emulates the achievement of Olympic gold medallist Nicola Adams, who won the title in 2011.
"To be European champion this early in my career is incredible," said Gale.
"I am still learning and am so excited for what is still to come."
England's Natasha Gale won middleweight gold at the European Women's Boxing Championships, beating Maily Nicar of France in the final.