Mark Johnston (born 10 October 1959) is a Scottish racehorse trainer based in Middleham, North Yorkshire, England.

He started training at a stable near Louth, Lincolnshire in 1987, and his first winner was Hinari Video at Carlisle[1] He has been training in Middleham since 1988 when he purchased Kingsley House (often falsely attributed to be the former home of Charles Kingsley, author of The Water Babies).

Johnston's horses are known for their front running style and bravery in a finish, two attributes that were best advertised by the exploits of Attraction.

[1] On 23 August 2018 Johnston became the most successful British Flat trainer of all time when Frankie Dettori rode Poet's Society to win the 3.00 at York at odds of 20–1 to give Mark his 4,194 winner.

[2] In January 2022 Johnston's son and assistant trainer, Charlie, joined him as joint training licence holder.