Merga Bien (late 1560s – 1603) was an alleged German witch, perhaps the most famous of the many victims in the great mass Fulda witch trials in Germany in 1603–1605.
Bien was born in the city of Fulda. She was married three times and was the heiress of her first two husbands, which was later an important part of the accusations of her. In 1588, she married Blasius Bien and moved from the city, but returned after a conflict with her husband's employers.
This was during the reign of the Prince-bishop Balthasar von Dernbach. A Catholic fanatic, he ordered an investigation of witchcraft in the city as a lead in his counterreformation after his accession in 1602. Over two hundred people were executed for witchcraft in the great witch trial, which lasted the three years he was in power, until his death in 1605. Merga was to be one of the first victims.
In March 1603, the investigations resulted in the first wave of arrests in the city. On 19 June, Merga was arrested and put in jail. Her husband protested before the court in Speyer and pointed out that she was pregnant.
In jail, she was forced to confess to the murder of her second husband and her children with him and one member of the family of her husband's employers, and that she had taken part in a sabbath of Satan. Her pregnancy was considered an aggravating circumstance; she and her husband had no children although they had been married for fourteen years, which raised the suspicion that they had used contraception. She was forced to confess that her current pregnancy was the result of intercourse with the Devil.
Bien was judged guilty of witchcraft and was burned alive at the stake in Fulda in the autumn of 1603.
On 15 March 1605, the Prince bishop Balthasar von Dernbach died, ending his reign over the bishopric of Fulda.