This is the first new bomber in 30 years and could cost nearly $700 million.
It can carry nuclear and conventional weapons.
The specific details of the aircraft are still being kept under wraps.
But US Defense Secretary Lloyd Austin said it was “evidence of America’s continued superiority in ingenuity and innovation”.
The B-21 Raider was unveiled at a ceremony at the manufacturer’s Northrop Grumman plant in California.
Austin said the aircraft would represent a significant advance over existing bombers in the US Navy, noting that “even the most advanced air defense systems will have difficulty detecting the B-21 in the sky.”
“Fifty years of low-surveillance technology has been incorporated into this aircraft,” he said.
He added that the aircraft was also built with an “open system architecture” that allows it to incorporate “new weapons that haven’t been invented yet.”
While the potential for unmanned flight was not mentioned at the ceremony, a US Air Force spokesman said the aircraft “had the capability, but no resolve, to fly unmanned.”
The maiden flight of the B-21 is scheduled for next year.
It will replace the B-1 and B-2 models and the fleet is estimated to cost $203 billion to develop, acquire and operate over 30 years, according to Bloomberg.
Six aircraft are currently in production, the manufacturer said, adding that they will use “next-generation stealth” and that they will use unspecified “new production methods and materials”.
The US Air Force plans to purchase at least 100 aircraft.
