Samuel Geoghegan (born 1845 in Dublin, died 4 September 1928) was an Irish mechanical engineer.

Samuel Geoghegan was in 1861, according to the English census of that year, a pupil of a schoolmaster named Richard Biggs in Devizes, Wiltshire.^[1] He was then for three years an apprentice at the engineering company Walter May & Co of Birmingham and was afterwards a draughtsman with P. and W. MacLelland, and Howden & Co of Glasgow and a fitter with Fawcett, Preston & Co of Liverpool.^[2][3]

In 1869 he went to Smyrna in Turkey as a mechanic and draughtsman with the Ottoman Railway, and two years later he returned to England as a fitter in the Doncaster Locomotive Works of the Great Northern Railway.^[2]

In 1871 he went to India and was engaged on the construction of a bridge two miles long over the river Chenab in the Punjab, first as assistant engineer and then as executive engineer in charge of half the bridge. Subsequently, he was for a year a district locomotive superintendent on the railway near Delhi.^[2]

In 1874 he was appointed chief engineer to Arthur Guinness & Son of Dublin, and he retained this position until 1901, when he became consulting engineer to the company. In 1880 he became a Member of the Institution of Mechanical Engineers.^[2]

In 1882 he invented and patented a lightweight steam locomotive with all moving parts high above the dirty floor to fit within a 6 ft (1.8 m) loading gauge. He invented also a Haulage Wagon by which his patented narrow gauge locomotives could be used on broad gauge track.^[4]

By 1899, he had become head of the Guinness Brewery's electrical and mechanical engineering staff. He retired on 9 July 1901, at the age of 56, but was retained as a consultant until 11 February 1905. After his retirement, he ran a private practice from 17 Westland Row.^[1]

He had married in 1876 and had five children.^[1] He died on 4 September 1928.^[2]