A woman who cut off her husband's penis with a breadknife during a row was then stabbed to death by her partner.
The 37-year-old man, reportedly of Ghanaian origin, then had his severed organ sewn back on in hospital.
Police said the couple had been separated since the start of the month, but the fight broke out when the woman, aged 50, paid a visit to her husband.
Neighbours alerted police in the German city of Kassel after seeing the two fighting outside.
The man remains in custody in hospital, and his condition is not known.
The wife was also taken to hospital, but died of her injuries.