James Mansergh FRS (29 April 1834 – 15 June 1905) was an English civil engineer.

His candidature citation read: President of the Institution of Civil Engineers.

The designer of the waterworks and sewerage of Lancaster, Lincoln, Stockton, Middlesbrough, Rotherham, Southport, Burton-on-Trent, Melbourne (Australia), Birmingham, and many other towns.

These designs include some of the largest schemes of water supply, sewerage or sewage disposal for Halifax, Hereford, St Helens, Darlington, Whitby, the Potteries, Derby, Southampton, Durham, Shrewsbury, Malvern, Cambridge, Edinburgh, Plymouth, York, Antigua, Philadelphia (US), and other places.

[5]In March 1903 he received the honorary freedom of his native town of Lancaster.