Joan Parker, a prominent philanthropist and widow of best-selling mystery writer Robert Parker, passed away Tuesday after a lengthy battle with lung cancer. She was 80.

The longtime Cambridge resident was a powerhouse fundraiser for HIV and AIDS research. She was actively involved in her husband's literary career, even after his death in 2010.

In March, Joan invited Greater Boston into her home where Robert wrote dozens of novels. She also spoke openly about her advocacy for hospice care and end of life planning.