The project is part of the much-delayed visitor centre planned for the site, which is jointly run by the Highways Agency, English Heritage and the National Trust. The 2 km tunnel will reroute the A303 below the planned centre, designed by Denton Corker Marshall.
The tunnel will be the first major road project to go ahead using the Highway Agency's accelerated planning procedure, known as "early design and build", in which contractors are involved earlier than usual to encourage a shorter construction period. The joint venture will work with consultants Halcrow and Gifford on designs.
The Stonehenge announcement was one of three highway project decisions made last week. A joint venture between WS Atkins and Accord Jarvis won a seven-year, £190m maintenance contract with the Highways Agency for 560 km of motorways and trunk roads in Staffordshire, Leicestershire and Warwickshire.
Alfred McAlpine has won a seven-year deal, worth £200m, for 500 km of motorways and trunk roads in Derbyshire, Leicestershire, Lincolnshire and Nottinghamshire. McAlpine will be working in partnership with highways consultant Scott Wilson.
McAlpine also won three utilities contracts worth a total of £28.5m with Severn Trent Water, Yorkshire Water and Scottish Power.