Kyle, 38, served four tours in Iraq and was awarded two Silver Stars, five Bronze Stars with Valor, two Navy and Marine Corps Achievement Medals, and one Navy and Marine Corps Commendation.
From 1999 to 2009, Kyle recorded more than 150 sniper kills, the most in U.S. military history.
After leaving combat duty, Kyle became chief instructor training Naval Special Warfare Sniper and Counter-Sniper teams, and he authored the Naval Special Warfare Sniper Doctrine, the first Navy SEAL sniper manual. He left the Navy in 2009.
"American Sniper," which was published last year by William Morrow, became a New York Times best seller.
"We are devastated by the news of Chris Kyle's death," William Morrow executive editor Peter Hubbard said in a statement. "It was an incomparable honor to help share Chris's story of service and faith with the world. Chris was a hero as much on the home front as on the battlefield -- a man who dedicated his life in recent years to supporting veterans and donated the proceeds of American Sniper to the families of his fallen friends. He deserves our deepest respect. Our prayers are with his family and the entire military community. He will never be forgotten."
Kyle was also an advocate for his fellow service members suffering from PTSD, creating a foundation to help with their treatment.