The Siddeley Aircraft Company was a British aircraft manufacturer founded in 1916. It played a significant role in the development of military and civilian aircraft during the early to mid-20th century. The company was known for producing innovative designs, including the Siddeley S.R.1 and the Siddeley Whirlwind fighter aircraft. In 1920, Siddeley merged with Armstrong Whitworth to form the Armstrong Siddeley company, which continued to produce aircraft and engines. The company contributed to various aviation advancements and was involved in the production of engines for both military and commercial use until its eventual decline in the late 20th century.