Eastleigh, town and borough (district), administrative and historic county of Hampshire, southern England.
It lies north and east of Southampton, centred on the town of Eastleigh. The borough grew rapidly in the 19th century with the establishment of railway works. Eastleigh has become an area of contrasts, ranging from the town of Eastleigh, an expanding industrial annex of Southampton, through residential development to a yachtsmen’s playground at Hamble. Area borough, 31 square miles (80 square km). Pop. (2001) town, 52,894; borough, 116,169; (2011) town, 78,716; borough, 125,199.