Tapa cloth (or simply tapa) is a barkcloth made in the islands of the Pacific Ocean, primarily in Tonga, Samoa and Fiji, but as far afield as Niue, Cook Islands, Futuna, Solomon Islands, Java, New Zealand, Vanuatu, Papua New Guinea and Hawaii (where it is called kapa). In French Polynesia it has nearly disappeared, except for some villages in the Marquesas. In Melville's Typee, the ship Dolly enters the harbor of Nukuheva where it is met by "swimming nymphs ... their adornments were completed by passing a few loose folds of white tappa, in a modest cincture, around the waist."

The word tapa is from Tahiti and the Cook Islands, where Captain Cook was the first European to collect it and introduce it to the rest of the world. The cloth is also known by a number of local names, although the term tapa is international and understood throughout the islands that use the cloth. In Tonga, the same cloth is known as ngatu, and it is of great social importance to the islanders, often being given as gifts. In Samoa, it is called siapo, and in Niue it is hiapo. In Hawaii, it is known as kapa. In Rotuma, a Polynesian island part of Fiji, it is called ʻuha and in other Fijian islands it is called masi. In the Pitcairn islands it was called 'ahu, and in New Zealand was known as aute. It is also known as tapia.

During voyages of migration the paper mulberry tree (Broussonetia papyrifera) known as hiapo or siapo was introduced from Southeast Asia. Tapa cloth was present in Western Polynesia (Fiji, Tonga and Samoa) by about 1000 AD and then spread throughout the Pacific as people voyaged to islands further afield. Tapa also has the meaning of border or strip. It seems likely that before the glueing process became common to make large sheets (see below) only narrow strips were produced.

Tapa can be decorated by rubbing, stamping, stencilling, smoking (Fijian: masi kuvui, "smoked barkcloth") or dyeing. The patterns of Tongan, Samoan and Fijian tapa usually form a grid of squares, each of which contains geometric patterns with repeated motifs such as fish and plants, for example four stylised leaves forming a diagonal cross. Traditional dyes are usually black and rust-brown, although other colours are known.

In former times the cloth was primarily used for clothing, but now modern textiles have replaced it. The major problem with tapa clothing is that the tissue loses its strength when wet and falls apart. However, it was better than grass skirts, which usually are either heavier and harder or easily blown apart. Tapa is also labour-intensive to manufacture. Tapa cloth was made by both men and women in ancient times, for example in Hawaii.

Nowadays tapa is often worn on formal occasions such as weddings. Another use is as a blanket at night or for room dividers. It is highly prized for its decorative value and is often found hung on walls as decoration. It has been used in ceremonial masks in Papua New Guinea and the Cook Islands (Mangaian masks). It was used to wrap sacred objects, e.g., "God staffs" in the Cook Islands.

In some places, artists are reviving tapa-making and creating modern interpretations of the art using new techniques or designs.

Tapa cloth is or ngatu still a part of daily life in Tonga. In Tonga a family is considered poor, no matter how much money they have, if they do not have any tapa in stock at home to donate at life events like marriages, funerals and so forth. If the tapa was donated to them by a chief or even the royal family, it is more valuable.