Sir William Lyons (4 September 1901 – 8 February 1985), known as "Mr. Jaguar", was with fellow motorcycle enthusiast William Walmsley, the co-founder in 1922 of the Swallow Sidecar Company, which became Jaguar Cars Limited after the Second World War.

In 1921, Lyons met William Walmsley who was converting army-surplus motorcycles for civilian use and making sidecars. Lyons admired the sidecars and bought one. Lyons and Walmsley obtained from their fathers a substantial £500 bank guarantee to go into business. Their plans were delayed as Lyons was under the legal age, but on his 21st birthday he formed a partnership with Walmsley. It was called Swallow Sidecars and had a staff of "three men and a boy".

The first "Jaguar" model was offered in 1935, and after World War II, Lyons changed the company name to Jaguar to avoid the unfortunate connotations with the Nazi SS "Schutzstaffel". Armstrong Siddeley allowed Lyons to use the Jaguar name from their successful aircraft engine range, such was the camaraderie of the car industry at the time.
In 1956, Lyons was knighted for his services to British industry and for the fine export performance of the company. In 1966, faced with a strengthening global industry, he merged Jaguar with the British Motor Corporation (BMC) to form British Motor Holdings, which was later absorbed into British Leyland. 

According to en.wikipedia

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