John Foulston (1772 – 30 December 1841) was an English architect who was a pupil of Thomas Hardwick and set up a practice in London in 1796.

[1] Most of Foulston's work was in the Greek Revival style, but his best known project was the creation of a group of buildings in Ker Street, Devonport in 1821–24.

[1] The theatre was notable for being one of the first buildings in Britain to use cast and wrought iron for parts of its main structure; it was demolished just before World War II to make way for a cinema.

[11] In 1818 he designed the asterisk-shaped Cornwall County Asylum at Bodmin, later known as St Lawrence's Hospital, and now a Grade II* listed apartment building.

[15] In his later years he created an elaborate water garden at his home (Athenian Cottage in the suburb of Mutley[2]), and he was wont to drive round the streets of the town in a gig disguised as a Roman war chariot.