The army said on Thursday troops rescued Lydia Simon with her three children in Gwoza district in northeast Borno State.
“Lydia was five months pregnant at the time of her rescue and claimed to be from Pemi Town in Chibok,” the authorities said.
The statement was accompanied by a picture of Simon and her children, who appear to be between the ages of 2 and 4.
The Chibok abduction shocked the world and triggered a global social media campaign tagged #BringBackOurGirls.
The Army didn’t say how she was freed other than that she was rescued in a hot spot known as Ngoshe in Borno.
The military has now recaptured large areas once held by Boko Haram, which has also been weakened by infighting with its more dominant rival, Islamic State West Africa Province (ISWAP).
More than 40,000 people have been killed and more than two million more displaced by the conflict since it began in 2009.
Mass abductions are still a major worry in Nigeria and kidnap gangs have often targeted schools to snatch students for ransom demands.
More than 1,680 pupils were kidnapped in Nigerian schools from early 2014 to the end of 2022, according to the charity Save the Children.
Last month more than 130 children were kidnapped from their school by gunmen in Kaduna state in one of the largest abductions in recent years.