Kelly said he wants to spend more time with his wife, Rep. Gabrielle Giffords, as she recovers from a gunshot wound to the head.
Most recently, he was commander of the Endeavour's final mission, which ended June 1. Kelly's decision is not surprising. NASA is retiring its space shuttle fleet in just another month, and it will be years before the United States has another spacecraft for astronauts to fly.
The couple is also working on a new memoir together. The book will reportedly be an intimate look at their careers and courtship.
It will also focus on the Jan. 8 tragedy when a gunman shot Giffords during a political event in Arizona.
It is unknown when the untitled book will be published.
Because of rules covering members of the House of Representatives, Giffords will not receive an advance against royalties and the deal must be cleared by the House ethics committee. Royalties derived from book sales are permitted, a portion of which will be donated to charities that benefit Tucson and Arizona. The percentage being donated and the specific charities have yet to be determined.
The Associated Press contributed to this report.