The Standard wet liner inline-four engine was an inline four cylinder petrol engine produced by the Standard Motor Company. Originally developed concurrently for passenger car use and for the Ferguson TE20 tractor, it was widely used for Standard passenger cars of the 1950s, most notably the Vanguard. Later it was successfully used in Standard's popular early generation Triumph TR series sports cars.

The Standard Motor Company Limited was a motor vehicle manufacturer, founded in Coventry, England, in 1903 by Reginald Walter Maudslay. For many years, it manufactured Ferguson TE20 tractors powered by its Vanguard engine. All Standard's tractor assets were sold to Massey Ferguson in 1959. Standard purchased Triumph in 1945 and in 1959 officially changed its name to Standard-Triumph International and began to put the Triumph brand name on all its products. A new subsidiary took the name The Standard Motor Company Limited and took over the manufacture of the group's products.