Some closures will take place from early on Saturday for the Mini and Junior BUPA great South Runs, plus the 5k event.
Sunday will see more streets in the south of the city closed as the main 10-mile event takes place. It will feature some of the world's best athletes as well as a record 30,000 club, fun and charity runners. Olympic gold medallist Dame Kelly Homes will be the honorary starter of the race, the world's leading 10-mile running event.
The race starts on Southsea seafront outside the D-Day museum and goes to Old Portsmouth, through the historic dockyard towards the city centre, along Winston Churchill Avenue and down towards the seafront again before a final turn from the Eastney end of the seafront back toward the D-Day Museum where it finishes. Local bands will be playing along the route, to encourage the runners.
Roads will re-open as quickly as possible. Queen Street and access to The Hard should be opened by 1.30pm on Sunday. Other roads en route will be opened as soon as they are clear of runners and water stations.
All city centre car parks will be open, and it's recommended that visitors, shoppers and spectators use these, as they are not on the route and will mean a quicker exit from the city.
Car parking will also be available on Southsea Common for competitors, officials, and spectators during Saturday and Sunday, but charges will apply (£3 per car). Parking on the common will be free for displaced residents with a valid residents' parking permit.
Full details of roads to be closed are at www.portsmouth.gov.uk