The M27 is a motorway in Hampshire, England. It is 25 miles (40 km) long and runs west-east from Cadnam to Portsmouth. It was opened in stages between 1975 and 1983. It is unfinished, as an extension to the east was planned. A number of smaller motorways were proposed, connecting the city centres of Southampton and Portsmouth to the motorway; of these only the M271 and M275 were built.