The woman -- who is awaiting a kidney transplant -- was crying in the audience of Williams' show Sunday, so the entertainer's security guards brought her backstage to meet with Williams, the celebrity news website said.
Williams was so moved by her story, he excused himself from the room, then reappeared moments later with a folded up sheet of paper that read, "God never leaves."
Inside the paper were 10 $100 bills.
TMZ spoke to the woman who expressed her gratitude for the "awesome surprise."
The celebrity news website did not disclose the woman's name.