A 59-year-old woman was grazed by a stray bullet as she sat on her porch in Brooklyn Tuesday night, cops and sources said. 

The innocent bystander was sitting outside her home on East 29th Street near Avenue D in Flatbush around 8:20 p.m. when shots rang out and an errant slug grazed her in the forehead, according to authorities and sources. 

She was taken to the Kings County Hospital Center, where she was listed in stable condition. 

The motive for the gunfire remained unclear Wednesday.

The violence came less than a week after a 71-year-old woman was killed and a 34-year-old woman wounded – both by stray bullets – in the Bronx, police said.

Also last week, an 8-year-old boy was wounded by a stray round a short time after he got off a school bus in the northernmost borough, cops said.