Yes, American Sniper is based on the true story of Chris Kyle - a former cowboy who is, to date, the most accurate and lethal marksman in US military history.
The film is directed by acclaimed actor and director Clint Eastwood.
Chris Kyle's kill count is officially the highest ever recorded (and unofficially he claimed to have killed many more):
160 confirmed kills
255 probable kills
Chris Kyle served in Iraq 4 times and won numerous awards and medals for his bravery. Military intelligence suggests enemy forces even put a $20,000 bounty on his head!
It could be considered kind of ironic then, that Chris didn't die in combat... But rather at a shooting range in Texas, at the hands of a fellow US soldier who was apparently suffering from Post-traumatic Stress Disorder.