A former student of Government Secondary School (GSS) Chibok in Borno State, and her husband, a Boko Haram member, have surrendered to the Nigerian military.
The girl and more than 250 others were abducted by insurgents in April 2014. Dozens remain missing.
Her identity is being concealed after she and her husband renounced membership of the sect.
They presented themselves to troops at a location around the Lake Chad region.
Release of remaining Chibok girls still work in progress – Presidency
Intelligence sources said their decision might have been prompted by increased operations by the Armed Forces, outbreak of killer diseases and food scarcity.
The couple are undergoing profiling at a military formation. Boko Haram and ISWAP fighters occasionally turn themselves in citing different reasons.