"Feeling pretty good," Fei said in the first broadcast comment from the astronauts.
The capsule entered its preset orbit 23 minutes after launch, the government announced.
State television showed Chinese President Hu Jintao watching the liftoff from a command center in Beijing, while Premier Wen Jiabao was on hand at the launch base.
"We await your triumphant return! Good luck!" a technician at mission control told the astronauts minutes before the liftoff.
Wen declared the launch a success.
"The Shenzhou 6, which has attracted worldwide attention, has successfully launched," the premier said.
'Pride to humankind'
The manned space program is a key prestige project for China's ruling Communist Party, which hopes that patriotic pride at its triumphs will help to shore up the party's public standing amid frustration at official corruption and social problems.
In Beijing, hundreds of people gathered on a plaza outside the Chinese capital's main train station to watch the launch on a giant television screen. Some clasped their hands in anxiety as the rocket surged skyward.
"The Shenzhou liftoff brings pride to our divine land, pride to our Chinese people, pride to our country and pride to humankind," said one man, who would give only his surname, Zhu.