Kathy Griffin's sister, Joyce -- the one stricken with cancer who inspired Kathy to shave her head in July -- has lost her battle.

Joyce Griffin succumbed to an undisclosed form of cancer after undergoing extensive chemotherapy.

You'll recall, 2 months ago Kathy shaved her head in solidarity.

It's been tough for Kathy. Her older brother, Gary Griffin, died of esophageal cancer in 2014. Another sibling of Kathy's also died young. She had 4 siblings. Now there are 2.

Joyce was 65 years old. RIP.