Lieutenant-Colonel Colquhoun Grant CB (1780 – 20 October 1829) was a British Army soldier and intelligence officer during the Napoleonic Wars.

Of a family from the Scots aristocracy, Grant, the youngest of eight brothers, was commissioned into the 11th Foot in 1795, reaching the rank of major by 1809 when he was posted to the Iberian Peninsula during the Peninsular War under the command of Arthur Wellesley, later Duke of Wellington.

In 1810 he was appointed to Wellesley's personal staff as an Exploring Officer in the Peninsula Corps of Guides, a special reconnaissance unit whose members spoke the local languages.

Grant was able to pass himself off as an American officer and spent some weeks at liberty in the streets and salons of Paris, sending intelligence reports to Wellington.

Grant sent in a steady stream of reports regarding the build-up of French troops along the border and returned to Brussels in time to take part in the Battle of Waterloo on 18 June.