A braid (also referred to as a plait) is a complex structure or pattern formed by interlacing three or more strands of flexible material such as textile yarns, wire, or hair.

The simplest and most common version is a flat, solid, three-stranded structure. More complex patterns can be constructed from an arbitrary number of strands to create a wider range of structures (such as a fishtail braid, a five-stranded braid, rope braid, a French braid and a waterfall braid). The structure is usually long and narrow with each component strand functionally equivalent in zigzagging forward through the overlapping mass of the others. It can be compared with the process of weaving, which usually involves two separate perpendicular groups of strands (warp and weft).

Historically, the materials used have depended on the indigenous plants and animals available in the local area. During the Industrial Revolution, mechanized braiding equipment was invented to increase production. The braiding technique was used to make ropes with both natural and synthetic fibers as well as coaxial cables for radios using copper wire. In more recent times it has been used to create a covering for fuel pipes in jet aircraft and ships (first using glass fibre, then stainless steel and Kevlar). Hoses for domestic plumbing are often covered with stainless steel braid.