The blue knife is a modern survival blade design that gained recognition in the late 20th century, though its roots are often described as a blend of older frontier and Native American tool concepts. The most widely known version was popularized by Tom Brown Jr., a wilderness survival instructor, and custom knife maker Ed Lombi in the 1980s. Brown promoted the design as a multi-purpose survival tool capable of chopping, carving, skinning, and even light sawing—functions traditionally spread across several tools.

The knife’s distinctive shape—featuring a curved blade with multiple edges and a heavy spine—was intended to allow users to perform a wide range of outdoor tasks with a single implement. It became more widely known after appearing in the 2003 film The Hunted, where Brown was involved in training and design consultation.