General John Longfield, CB (1805 – 27 February 1889) was an Irish senior officer in the British Army.
He was appointed an rnsign in the 8th (The King's) Regiment of Foot in 1825 and progressed through the ranks, becoming lieutenant in 1828, captain in 1835, major in 1844, lieutenant-colonel in 1846 and brevet colonel in 1854.
He commanded the 2nd Brigade at the Siege of Delhi, India in 1857 when his brigade was in reserve during the assault, and served in the city of Delhi during the following six days of fighting.
In 1860 he was promoted to major general and on 19 April 1868 was appointed colonel of the 29th Regiment of Foot.
A year later he was promoted to lieutenant-colonel and to full general on 19 July 1876.