A tarpaulin or tarp, is a large sheet of strong, flexible, water-resistant or waterproof material, often cloth such as canvas or polyester coated with polyurethane, or made of plastics such as polyethylene. In some places such as Australia, and in military slang, a tarp may be known as a hootch. Tarpaulins often have reinforced grommets at the corners and along the sides to form attachment points for rope, allowing them to be tied down or suspended.

Inexpensive modern tarpaulins are made from woven polyethylene; this material is so associated with tarpaulins that it has become colloquially known in some quarters as polytarp.

Tarpaulins are used in many ways to protect persons and things from wind, rain, and sunlight. They are used during construction or after disasters to protect partially built or damaged structures, to prevent mess during painting and similar activities, and to contain and collect debris. They are used to protect the loads of open trucks and wagons, to keep wood piles dry, and for shelters such as tents or other temporary structures.

Tarpaulins are also used for advertisement printing, most notably for billboards. Perforated tarpaulins are typically used for medium to large advertising, or for protection on scaffoldings; the aim of the perforations (from 20% to 70%) is to reduce wind vulnerability.

Polyethylene tarpaulins have also proven to be a popular source when an inexpensive, water-resistant fabric is needed. Many amateur builders of plywood sailboats turn to polyethylene tarpaulins for making their sails, as it is inexpensive and easily worked. With the proper type of adhesive tape, it is possible to make a serviceable sail for a small boat with no sewing.

Plastic tarps are sometimes used as a building material in communities of indigenous North Americans.Tipis made with tarps are known as tarpees.

Tarpaulins can be classified based on a diversity of factors, such as material type (polyethylene, canvas, vinyl, etc.), thickness, which is generally measured in mils or generalized into categories (such as "regular duty", "heavy duty", "super heavy duty", etc.), and grommet strength (simple vs. reinforced), among others.

Cut Size refers to the size of a tarp before sewing of seams and hems. As an example, for a 6' x 8' Cut Size tarp, the material will start at 6' x 8'. After sewing, it will finish approximately 5'6" x 7'6". Generally, you will lose 6-9" per dimension depending on the size of the piece and the number of seams needed to fabricate the piece. 3" of fabric is needed to make a hem, plus additional material is needed to sew the panels together.

Conversely, Finish Size refers to the size of a tarpaulin after sewing (hem) has been completed. This means that if the Finish Size is specified when ordering, the extra fabric that is necessary to create hems and seams has already been accounted for and the actual end product will be 6' x 8'. As such, a 6' x 8' Finish Size tarp will finish at 6' x 8' after sewing is completed. In other words, the material will start larger, approximately 6'6" x 8'8" and then after the hems and seams are made, the piece will be 6' x 8' when completed.