The Avonside Engine Company was a locomotive manufacturer in Avon Street, St. Phillips, Bristol. The company was formed in 1864 to take over the business of Slaughter, Gruning and Co. The directors were John Bates, William Bevan, Henry Gruning, George Edgar Ranking, Edward Slaughter (Managing Director) and Christopher James Thomas. Company's purpose was the construction and maintenance of locomotive and marine engines. In 1881 the company went into liquidation during a recession in the industry.