The 43-year-old man phoned emergency services at 9.30am on Wednesday and said his partner had fallen asleep after they got drunk the night before.
He said they had both consumed a lot of alcohol and when he woke he noticed the 52-year-old woman showed no signs of life.
But police arrested him later that day at his home in Kleinhadern, south-west Munich, after injuries were found on the woman’s body.
Police said they also saw signs of violence in the apartment.
An autopsy was carried out on Wednesday afternoon confirming the woman died a violent death.
The man was then arrested on suspicion of manslaughter.