English: Sir John Benjamin MacNeill (1793 - 2 March 1880) was an eminent Irish civil engineer of the 19th century, closely associated with Thomas Telford. His most notable projects were railway schemes in Ireland.

During the late 1830s and early 1840s, MacNeill focused on his native Ireland. He worked on various railway projects, including the Dublin and Drogheda Railway, including plans to extend the railway beyond Drogheda towards Portadown. Much of Ireland’s modern railway network still follows routes he proposed. For example, the Dublin-Belfast railway line follows the line of the Dublin and Drogheda Railway along the coast (MacNeill was knighted in 1844 following its completion) and many of its impressive original structures remain (e.g.: the 98 ft high Boyne Viaduct built between 1851 and 1855 near Drogheda, the 18-arch, 126 ft high Craigmore Viaduct near Bessbrook and the nearby MacNeill's Egyptian Arch).

In April 1860, MacNeill was appointed engineer of the Londonderry and Lough Swilly Railway, intended to link Lough Foyle and Lough Swilly across the Inishowen peninsula in north Donegal. It was around this period that the Victorian’s enthusiasm for railways began to wane, and the Lough Swilly company was one of many that rarely made a profit. This was disastrous for MacNeill as many of his commissions were to be rewarded through share dividends on any profits. With his income dwindling, MacNeill became impoverished and – after a fire destroyed his home - he moved to London. He later became blind, dying at his son's house in Cromwell Road, south-west London on 2 March 1880.

A commemorative plaque was unveiled on 20 July 2001 at his (previously) unmarked grave in Brompton Cemeteryin London