A fascine knife (or gabion knife) is a side arm / multipurpose tool used by 17th-19th century light infantry and artillery. It was named for its use as a tool for cutting fascines (bundles of sticks used to strength the sides of trenches or earth ramparts protecting artillery batteries); it was also a personal hand-to-hand weapon.

There is no set pattern to the fascine knife - older versions are similar to cavalry swords, but later examples resemble billhooks in shape and appearance. Spanish examples are known as machetes but do not resemble the modern-day appearance of that tool.