The USS Minnesota (SSN 783) is more than 90 percent complete, the company said.
"Launch is a significant accomplishment in the life of a submarine," said Jim Hughes, NNS vice president of submarines and fleet support. "It's an opportunity for our incredible shipbuilders to stand back and take pride in their work.
"Thanks to their tremendous efforts and steadfast determination, Minnesota's progress is nearly one year ahead of schedule and has been built using about 600,000 fewer man-hours than the previous boat."
The Minnesota is the 10th submarine of its class. Construction of the submarine began in 2008.
For the launch into the James River in Virginia the Minnesota, a 7,800-ton vessel, was moved from the NNS facility into a floating dry dock using a transfer car system and then submerged.
The vessel was moved by tugboats to a submarine pier for the final stages of outfitting and testing.