Long tailbacks built up on the A3M after a collision involving eight cars.
The accident happened at 8.25am on the northbound carriageway of the motorway near Clanfield. Police said no one has been hurt but it may take a while for all the vehicles to be moved. One lane is blocked.
It is not known how the accident happened. Highways Agency staff at the scene said there were delays of up to 15 minutes.