He will be accompanied by Mark Bezos, his brother, Wally Funk, an 82-year-old pioneer of the space race, and an 18-year-old student.
"I'm excited. People keep asking me if I'm nervous. I'm not really nervous, I'm curious. I want to know what we're going to learn," Bezos said in an interview with CBS News.
"We've been training. This vehicle's ready, this crew is ready, this team is amazing. We just feel really good about it."
Ms Funk commented: "It's going to happen! I've waited a long time and I've dreamed a long time to get to go up." She said she would carry out somersaults and tumbles while weightless in space.
In the 1960s, Ms Funk was one member of a group of women called the Mercury 13, who underwent the same screening tests as male astronauts, but who never got to fly into space.
At shortly after 14:00 BST (09:00 EDT), the four passengers will lift off on a rocket from Bezos' private launch site near Van Horn, Texas.