The Lappa Valley Railway is a 15 in minimum gauge railway located near Newquay in Cornwall. The railway functions as a tourist attraction, running from Benny Halt to East Wheal Rose, where there is a leisure area with two miniature railways.

Fifteen-inch gauge railways were pioneered by Sir Arthur Percival Heywood who was interested in what he termed a minimum gauge railway for use as estate railways or to be easy to lay on, for instance, a battlefield. In 1874, he described the principle behind it as used for his Duffield Bank Railway, distinguishing it from a "narrow-gauge" railway. Having previously built a small railway of 9 in gauge, he settled on 15 in gauge as the minimum that he felt was practical.