strait of the English Channel, between the mainland coast of the county of Hampshire, England, and the northwestern coast of the Isle of Wight. It extends eastward for 15 miles (24 km) from The Needles, a group of rocks west of the Isle of Wight, to Southampton Water, an inlet serving the port of Southampton; its breadth is between 1.75 and 4 miles (3 and 6 km). The strait is the submerged valley of a former eastward-flowing river of which the present Frome was headstream and the Itchen and Test were tributaries. East of The Solent, Spithead, the drowned eastern portion of the same valley, affords a safer approach to Southampton for large vessels. The mainland low coast is broken by the estuaries of the Beaulieu and Lym rivers; the coast of Wight, which rises more steeply, is cut by the Medina, Newton, and Yar estuaries.

Opposite The Needles there extends from the mainland a pebbly bank, nearly 2 miles in length, on the end of which stands Hurst Castle, dating from the 16th century. At the mouth of Southampton Water, another spit also bears a Tudor fortress, Calshot Castle. The Solent is the scene of yacht races, especially from the port of Cowes on the Isle of Wight, and is famous for the naval reviews off Spithead.