The Bentley 8 Litre was a large inline 6-cylinder luxury car made in various configurations by Bentley Motors Limited at Cricklewood, London. Announced 15 September 1930, it was also the last completely new model by Bentley before the company's financial collapse and forced sale to Rolls-Royce Limited.

A Bentley 4 Litre featuring a 4-litre, inline-6 engine in a shortened chassis was announced on 15 May 1931.

Introduced a year into the Great Depression, the 8-litre and its smaller 4-litre sibling were unable to turn the company's finances around. Less than nine months after the 8-litre's introduction, Bentley Motors was placed into receivership.

The straight-six engine used a one-piece cast-iron block and non-detachable cylinder head with a crankcase made from Elektron, a magnesium alloy. It featured an overhead camshaft driven by a Bentley patented "three-throw drive" system of triple coupling rods with, like all earlier Bentleys, four valves per cylinder and twin-spark ignition (separate coil and magneto systems), which were state-of-the-art at the time. The engine had a bore of 110 mm (4.3 in) and a stroke of 140 mm (5.5 in), giving a capacity of 7,983 cc (487.2 cu in). Pistons were of an aluminium alloy.

Both engine and gearbox were mounted each at three points on rubber to isolate the chassis and body from vibration.

An entirely new design of four-speed gearbox provided four speeds (constant mesh third) and reverse with a single-plate dry clutch which sent power through a hypoid bevel final drive to the rear axle and its 21" Rudge-Whitworth wire centre-lock wheels.

The 8 Litre was built on Bentley's largest rolling chassis, a ladder frame with large tubular steel crossmembers downswept from the front and rear axles towards the centre to lower the centre of gravity.

Neither engine nor gearbox contributed to the bracing of the chassis.