A serial rapist who has struck fear in the hearts of Harlem women has left plenty of DNA at his crime scenes, but it hasn’t matched anyone in the police database, sources said yesterday.

The sex fiend’s reign of terror on Sugar Hill and Hamilton Heights continued Monday when he raped his fourth victim at knifepoint since Aug. 1.

Cops have flooded the area with uniformed and plainclothes officers and are circulating a sketch of the rapist. They have also offered a $12,000 reward.