Venus Williams won her 47th WTA singles title as opponent Garbine Muguruza pulled out of the Wuhan Open final with an ankle injury when trailing 6-3 3-0.
Both players came into the tournament less than fully fit, with Williams, 35, struggling with a thigh problem.
The American, a seven-time Grand Slam champion, used her experience to good effect in the first set of the final.
She broke Wimbledon finalist Muguruza twice in the second set before the 21-year-old Spaniard withdrew.
"I'm very sorry to have had to retire, but sometimes the body just doesn't recover," said Muguruza.
Williams, who was taken to three sets by Britain's Johanna Konta in the quarter-finals and Italian Roberto Vinci in the semi-finals, made a slow start but her superior hitting helped her go 4-2 up.
Both players exchanged breaks of serve before world number 25 Williams closed out the set.
Muguruza's movement was hampered by the start of the second set and errors began to creep into her game before she retired.
Meanwhile, Britain's Heather Watson was beaten 6-3 6-4 in the second round of qualifying for the China Open by Ukraine's Kateryna Bondarenko.