Millbrook is a small village and civil parish near Bedford, England. It has a population of 130, increasing to 147 at the 2011 Census. Millbrook railway station, on the Marston Vale Line, is about two miles (3 km) from the village. The parish church, dedicated to St Michael and All Angels, is Grade II* listed.

The vale adjoining Millbrook is reputed to be the location that inspired the 'Slough of Despond' in John Bunyan's The Pilgrim's Progress.

Millbrook is also home to the Millbrook Proving Ground and The Millbrook Golf Club, formerly Lyshott Heath Golf Club.

Modelled on the Milford Proving Ground operated by General Motors (GM) in Michigan, Millbrook was opened in the 1960s by the GM subsidiary Bedford before passing over to Vauxhall. Due to the geographical needs of a full testing centre, including both hills and flat land, the traditional choice of a former Royal Air Force airfield was ruled out and many sites around the UK were surveyed before the location at Millbrook was decided upon, especially due to having the benefit of being close to Vauxhall's production site at Luton.

Construction of the Proving Ground began in 1968, and once the facility opened in 1970 it acted as the testing site for many European GM models from, among others, the Vauxhall and Bedford companies.

With Bedford withdrawing from the bus and truck markets in December 1986, Millbrook was put up for sale by GM. In 1988 the site was transferred to a new company, Millbrook Proving Ground Limited as part of Lotus and began to offer its facilities as well to non-GM companies. With the sale of Lotus in 1993 Millbrook was transferred to GM Holdings UK Limited, as an independently managed company and began to diversify into all aspects of vehicle testing including emission control. In October 2013, the proving ground was purchased by Rutland Partners. In September 2016 it was sold to Spectris.

• The centre provides vehicle test and development facilities including:
• Vehicle and system assessment
• Powertrain development
• Safety testing.