Tiabendazole (INN, BAN), also known as thiabendazole (AAN, USAN) or TBZ and the trade names Mintezol, Tresaderm, and Arbotect, is a preservative, an antifungal agent, and an antiparasitic agent.

Tiabendazole is used primarily to control mold, blight, and other fungal diseases in fruits (e.g. oranges) and vegetables; it is also used as a prophylactic treatment for Dutch elm disease. ^{[citation needed]}

Tiabendazole is also used as a food additive, a preservative with E number E233 (INS number 233). For example, it is applied to bananas to ensure freshness, and is a common ingredient in the waxes applied to the skins of citrus fruits. It is not approved as a food additive in the EU, Australia and New Zealand.

Use in treatment of aspergillosis has been reported.

It is also used in anti-fungal wallboards as a mixture with azoxystrobin.^{[citation needed]}

As an antiparasitic, tiabendazole is able to control roundworms (such as those causing strongyloidiasis), hookworms, and other helminth species which infect wild animals, livestock, and humans. First approved for use in sheep in 1961 and horses in 1962, resistance to this drug was first found in Haemonchus contortus in 1964, and then in the two other major small ruminant nematode parasites, Teladorsagia circumcincta and Trichostrongylus colubriformis.

Tiabendazole acts as a fungicide through binding fungal tubulin. Resistant Aspergillus nidulans specimens were found to have a mutation in the gene coding for β-tubulin, which was reversible by a mutation in the gene for α-tubulin. This showed that thiabendazole binds to both α- and β-tubulin.

This chemical is also used as a pesticide, including to treat Beech Leaf Disease.