The fire broke out around 5 a.m. Monday morning, gutting the motorhome parked on Bethel Island in the Delta.
Both people inside escaped, but not before being badly burned. One woman was burned over 80 to 100 percent of her body; a second person has burns over 20 percent of his or her body.
"Both victims were treated at the scene and flown to UC Davis Medical Center with their injuries by helicopter," said East Contra Costa County Fire Dept. Chief Hugh Henderson.
It took crews about 20 minutes to put out the fire which spread to a wood pile nearby, but caused no other major damage.