Austin 18/24

The Austin 18-24 (or 18-24 hp) is a large 5-litre luxury motor-car that was produced by the British manufacturer Austin. Despite the name, its successive engines rated around 30 horsepower for tax purposes and the pundits of the day regarded it as really a 30–40. It was launched in 1907 with the 25-30's 5.3-litre (4½ x 5 inches) engine and in Austin's catalogue replaced the 15-20, of which only four were made. The next year it used the 15-20's 4.4-litre engine.

In June 1920 The Times referred to it as (Austin's) ". . . famous 18-hp of years ago". The 18-24 was the first big seller for Austin, reaching sales of 1,566 by the end of 1913.

It was in fact replaced for 1914 by the 6.1-litre 30.6 tax horsepower Austin 30 hp. though the catalogue showed a new 20-hp described by the same pundits with the note "20 hp is a very fair estimate of its ranking".