The one-horse shay is a light, covered, two-wheeled carriage for two persons, drawn by a single horse. The body is chairlike in shape and has one seat for passengers positioned above the axle which is hung by leather braces from wooden springs connected to the shafts.
The one-horse shay is colloquially known in the USA as a 'one-hoss shay'.
A smaller and more lightly constructed version of the one-horse shay is called a chair or 'whiskey' because it can "whisk" around other carriages and pass them quickly. Another version of the 'whiskey', known as a 'whisky', is constructed exceptionally light in weight for the purpose of allowing it to be drawn by small ponies or light horses.
American writer Oliver Wendell Holmes Sr. memorialized the shay in his satirical poem  "The Deacon's Masterpiece or The Wonderful One-Hoss Shay". In the poem, a fictional deacon crafts the titular wonderful one-hoss shay in such a logical way that it could not break down. The shay is constructed from the very best of materials so that each part is as strong as every other part. In Holmes' humorous, yet "logical", twist, the shay endures for a hundred years (amazingly to the precise moment of the 100th anniversary of the Lisbon earthquake shock) then it "went to pieces all at once, and nothing first, — just as bubbles do when they burst". It was built in such a "logical way" that it ran for exactly one hundred years to the day.
In economics, the term "one-hoss shay" is used, following the scenario in Holmes' poem, to describe a model of depreciation, in which a durable product delivers the same services throughout its lifetime before failing with zero scrap value. A chair is a common example of such a product.
- Maine League of Historical Societies and Museums (1970). Doris A. Isaacson, ed. Maine: A Guide 'Down East'. Rockland, Me: Courier-Gazette, Inc. p. 160.
- "Jane Austin Society of North America Northern California article "Transports of Delight, How Jane Austen's Characters Got Around" by Ed Ratcliffe". Retrieved 2013-05-30.
- "Traditional Two Wheel Carriages". Retrieved 2013-05-30.
- "Encyclopedia Britannica article - One Horse Shay". Retrieved 2013-05-30.
- "The One-Hoss Shay by Oliver Wendell Holmes with illustrations by Howard Pyle - discussion of the satire is contained in the explanatory note entitled "logic, logical...". Retrieved 2013-05-30.
- "OECD Glossary of Statistical Terms - One-Hoss Shay". Retrieved 2013-05-30.
- The "One-Hoss Shay" by Oliver Wendell Holmes with illustrations by Howard Pyle. Contains extensive explanatory notes
- The Deacon’s Masterpiece or The Wonderful "One-Hoss Shay": A Logical Story. Contains explanatory notes and poem info
- The Deacon’s Masterpiece or The Wonderful "One-Hoss Shay": A Logical Story. Contains discussion of a practical lesson that can be obtained from the poem
- The One-Hoss Shay public domain audiobook at LibriVox