Montague Ainslie (1790 – 1 February 1884) was an English forester and businessman whose interests included the iron ore company Harrison Ainslie.
Ainslie was educated at Hawkshead Grammar School. In the early nineteenth century, he inherited the Grizedale Estate from his parents, Henry Ainslie and Agnes Ford. In 1841 he converted Ford Lodge into a larger residence which became known as Grizedale New Hall. Like his parents before him, he planted vast numbers of larch trees in the valley, continuing the development and growth of Grizedale Forest.
He built Ford House in Ulverston for his son, William George Ainslie, who was chairman and major shareholder of the North Lonsdale Iron and Steel Company. William became the first MP for Lonsdale and moved to London in 1865, after which Montague used Ford House as a town house from which to manage his business interests which included Harrison Ainslie, another Iron company and also an operator of shipping from Ulverston. Ford Park is now a community facility for residents of Ulverston.