In 'The Martian', what is the name of the astronaut left behind?

In “The Martian,” the astronaut left behind is Mark Watney.

Watney is an American astronaut, botanist, and mechanical engineer on NASA’s Ares III mission to Mars. During an evacuation caused by a powerful dust storm, flying debris strikes him and separates him from the rest of the crew. Believing he has died, the crew launches for orbit without him.

Watney survives and wakes inside the mission’s surface habitat, known as the Hab. With limited food, equipment, and communication, he applies engineering, chemistry, and agriculture to stay alive. One of his best-known survival projects is growing potatoes using stored supplies and Martian soil.

The name Mark Watney belongs to the character in Andy Weir’s novel and its 2015 film adaptation. Matt Damon played Watney in the movie, which is why “Matt Damon” is a tempting but incorrect answer: it is the actor’s name, not the astronaut’s. Lewis is the mission commander, while Beck is another crew member.