Anna Sophia of Brandenburg was born on 18 March 1598 in Berlin as the eldest daughter of Johann Sigismund of Brandenburg and Anna of Prussia.
Not much is known of her youth. She was only 16 years old when she married Duke Frederick Ulrich of Brunswick-Lüneburg, who was seven years her senior. It must have been an unhappy marriage as Anna Sophia had a love affair with Franz Albrecht of Saxe-Lauenburg, who was serving in the army. Letters of Anna Sophia and Friedrich were discovered. Anna Sophia reacted by fleeing to her brother, who was now the Elector of Brandenburg before writing to Emperor Ferdinand II. Frederick informed his wife that his affection had diminished and he was advised to leave her. The couple had no children, and Johann began seeking a divorce.
However, Anna Sophia would not consent to a divorce, effectively banning him from being able to marry again. Frederick instructed churches to exclude Anna Sophia from their prayers, and he refused to pay for her expenses. The Emperor should have intervened in this case, but he left the case until 1626. With negotiations finally underway, Frederick died suddenly in 1634, only 43 years old.
She died on 19 December 1659, and she is buried in the Berlin Cathedral.