A catlin was a long, double-bladed knife used for surgery, commonly amputations. It was common in the 17th-mid 19th century; thereafter its use declined in favor of mechanically-driven (and later, electrically driven) oscillating saws.
Surgeon William Clowes (1544–1604) wrote about the instrument in a medical treatise written in 1596, that amputation required the use of "a very good catlin, and an incision knife,"  Later, surgeon John Woodall referred to a "catlinge" in a work in 1639. By 1693, when British navy surgeon John Moyle described proper amputation techniques, he wrote that "with your Catling, divide the Flesh and Vessels about and between the bones, and with the back of your Catling, remove the Periosteum that it may not hinder the saw, nor cause greater Torment in the Operation,".
The term was thereafter understood to refer to an interosseous knife.
- In the Napoleonic War Aubrey-Maturin series by Patrick O'Brian, surgeon Stephen Maturin makes frequent use of a catlin to operate.
- In a scene in the 1993 movie Gettysburg, a battle medic is briefly seen holding a catlin.
- John Kirkup, The Evolution of Surgical Instruments: An Illustrated History from Ancient Times to the Twentieth Century (Norman Publishing, 2006), p381
- Id. at 382