Sack cloth is a coarse brown cloth made of natural fibre and used to make sacks or constrain bales of loose produce. It is breathable and thus resists condensation and associated spoilage issues of its contents; it is strong and durable enough to withstand rough handling in transit. It is also known as hessian or hessian cloth. In America, it is known as burlap.

Sack cloth also has a religious context, particularly in regard to penitence; see hairshirt.