Wessex Water will be closing Claverton Hill to traffic from 18 August for around eight weeks.
The road will be closed between The Lodge and Vineyards Cottage to allow the company to carry out water supply improvement work.
Students, staff and visitors who regularly use the road to access the A36 will have to follow a local diversion via Norwood Avenue, Claverton Down Road and Brassknocker Hill.
However, access for cyclists and pedestrians on Claverton Hill will be maintained throughout the work.
Wessex Water has agreed to temporarily reopen the road for one day on Saturday 14 September to allow it to be used by traffic leaving the University’s Open Day.