General Thomas Henry Johnston (died 1891) was a British Army officer.

Johnston was commissioned as an ensign in the 66th Regiment of Foot on 21 February 1822.

[1] Promoted to lieutenant-colonel on 28 December 1838, he commanded his regiment during the Lower Canada Rebellion.

[1] He was the Colonel of the 87th (Royal Irish Fusiliers) Regiment of Foot from 1864 to 1870.

[2] He then transferred to be Colonel of the 66th (Berkshire) Regiment of Foot from 1870 until it was amalgamated with the 49th Foot to form the Princess Charlotte of Wales's (Berkshire Regiment) in 1881, after which he was Colonel of the 2nd Battalion of the new regiment until his death in 1891.