Louis Harper (fl. 1879–1903) was a civil engineer from the north-east of Scotland who designed a number of suspension footbridges towards the end of the 19th century.
His father John Harper came from Turriff in Aberdeenshire, and worked as a fencer in Edinburgh and Glasgow before starting the family firm in Aberdeen in 1856, which became Harpers Ltd in 1885. John Harper patented a mechanism for straining wire, used both to make fences and later also for the cables of bridges. His son John took charge of the business until 1887, while his second son Louis served an apprenticeship with Jenkins & Mar, Civil Engineers.
Louis set up his own firm in 1889, later collaborating with the contractors James Abernethy & Co. In addition to his bridge projects, he assisted Aberdeen Council in surveying their town water scheme. He became an Associate Member of the Institution of Civil Engineers in 1893, resigning in 1921.
The firm's early bridges included suspension bridges at Aboyne, spanning 300 feet (91 m), and at Shocklach in Cheshire, both built in 1871. Neither bridge exists today. The early bridges had wooden towers, although these were replaced in later bridges by structural steel or cast iron members.
A number of other bridges are proposed as having been designed by Louis Harper at the Harper Bridges website, although in the absence of clear documentary evidence, they are not listed above.