Battle Angel

Set in the 26th century, the story takes place 300 years after a societal collapse caused by a major war. In that society, it's a technological dark age following a pinnacle of achievement far beyond where we are right now. Cyborg technology is a way of life. People are augmented a lot as workers, so being a cyborg is not unusual. The main character is a cyborg. She has an organic human brain, and she looks like she's about fourteen years old. She has a completely artificial body and she's lost her memory. She is found in a wreckage and reconstituted by a cyber-surgeon who becomes her surrogate father.