A serious crash involving three lorries and a car caused the closure of the M3 northbound.
The collision happened between junction 10 for Winchester at Bar End and junction 9 at Winnall just after 10:20 BST.
Initially all three lanes of the northbound carriageway were closed by police "for the rest of the afternoon", although one lane has since reopened.
One person was taken to hospital with serious injuries following the crash.
Motorists were told to avoid the area and delays of up to two hours were reported, with traffic tailing back to junction 13 for Eastleigh.
Surrounding roads, including in and out of Winchester and through Shawford, have also faced disruption.
The Hampshire and Isle of Wight Air Ambulance was called to the scene.
A spokesman for South Central Ambulance Service said one patient with serious injuries was taken to Southampton General Hospital, one patient with minor injuries to the Royal Hampshire County Hospital, Winchester, and a third patient with minor injuries was treated at the scene.