Police and ambulance crews were called to junction 8 eastbound at Bursledon at 7.40am to reports a woman had fallen from the bridge above the carriageway.
The woman was pronounced dead at the scene.
No-one else was injured, and a Hampshire Constabulary spokeswoman said the woman’s next of kin had been informed and were being supported by officers.
She added the death was not being treated as suspicious and a file is being prepared for the coroner.
There were major delays of over an hour on the eastbound route this morning after the incident.
All three lanes were closed but have now been reopened.