Cars introduced in 1921

The Morris Oxford Six is a motor car produced by Morris of the United Kingdom from 1921 until 1926, and again from 1929 until 1935. Initially produced as a straight-six engined version of the Morris Oxford bullnose, the original Oxford Six was the first car produced by Morris with a six-cylinder engine, but proved to be unreliable. The versions produced from 1929 onwards were introduced as a replacement for the Morris Oxford 16/40.

The Austin Twelve is a motor car introduced by Austin in 1921. It was the second of Herbert Austin's post World War I models and was in many ways a scaled-down version of his Austin Twenty, introduced in 1919. The slower-than-expected sales of the Twenty brought about this divergence from his intended one-model policy. The Twelve was announced at the beginning of November 1921 after Austin's company had been in receivership for six months. The number twelve refers to its fiscal horse power (12.8) rather than its brake horsepower (bhp) which was 20 and later 27. The long-stroke engines encouraged by the tax regime, 72 × 102 mm later 72 × 114.5 mm, had much greater low-speed torque than the bhp rating suggests.

The Bentley 3 Litre was a car chassis manufactured by Bentley. The company's first, it was developed from 1919 and made available to customers' coachbuilders from 1921 to 1929. The Bentley was very much larger than the 1368 cc Bugattis that dominated racing at the time, but double the size of engine and strength compensated for the extra weight. The 4000 lb (1800 kg) car won the 24 Hours of Le Mans in 1924, with drivers John Duff and Frank Clement, and again in 1927, this time in Super Sports form, with drivers S. C. H. "Sammy" Davis and Dudley Benjafield. Its weight, size, and speed prompted Ettore Bugatti to call it "the fastest lorry in the world", which was regarded as a compliment. Built in 3 main variants, Blue label, Red Label Speed models all carrying a 5-year warranty, and the coveted and rare Green Label 100 mph cars, which only carried a 12-month warranty reflecting the high state of tune.

The Charles Willetts Jnr Ltd company of Overend Road, Cradley Heath were a lifting tackle manufacturer who built a light car called the New British between 1921 and 1923 when tackle and winch work was slack.

The Novo was a Czech automobile prototype designed by Břetislav Novotný.

The Lecoy was a short lived British 4-wheeled cyclecar made from 1921 to 1922 by the Lambert Engineering Co Ltd, St Hilda's Works, Northolt Road, Harrow, Middlesex.

The Peugeot Type 156 was a large car announced in 1920 and produced between 1921 and 1923 by the French auto-maker Peugeot at their Sochaux plant. It was Peugeot’s first large car since before the First World War and its arrival recalled the Peugeot Type 135 which had ceased production in 1913. However, the 156 was larger and more powerful.

Peugeot Quadrilette is the popular name for the Peugeot Type 161 and Peugeot Type 172 and associated models produced between 1921 and 1924.

ALFA or later Alfa Romeo has made three cars named as 20/30 HP, first one 1910 4-cylinder 4-6-seater tourer, improved version 20/30 HP E in 1914 and 1921 the 20/30 HP ES Sport, a 4-seater sportscar.

Octo was a French automobile manufactured at Courbevoie by Louis Vienne between 1921 and 1928.