Liquid Air was the brand name of an unusual automobile planned by Liquid Air Power and Automobile Co. of London in 1899.
The first factory location was acquired in Boston, Massachusetts in 1899, and its owners claimed that they could construct a car that would run a hundred miles on liquid air. By 1901 the company had gone into receivership. In 1902 the product was demonstrated by its designer, Hans Knudsen, at a show in London; apparently the automobile that was shown was a modified Locomobile steamer. Here it was claimed to run 40 miles (64 km) at 12 mph (19 km/h) on 18 US gal (68 L; 15 imp gal) of liquid air, sold at a shilling a gallon.