The Avonside Engine Company was a locomotive manufacturer in Avon Street, St. Philip's, Bristol, England between 1864 and 1934. However the business originated with an earlier enterprise Henry Stothert and Company.

Stothert & Pitt was a British engineering company founded in 1855 in Bath, England. It was the builder of various engineering products ranging from Dock cranes to construction plant and household cast iron items. It went out of business in 1989. The name and intellectual property became part of Clarke Chapman.