International Code of Nomenclature
for algae, fungi, and plants

The International Code of Nomenclature for algae, fungi, and plants, known as “the Code,” is the set of internationally agreed rules and recommendations that govern the naming of these organisms.

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The naming of algae, fungi, and plants has deep historical roots. A major landmark was the publication in 1753 of Linnaeus's Species plantarum. The first actual code of nomenclature was Alphonse de Candolle's Lois de la Nomenclature Botanique (1867). It was followed by 17 editions under different titles, eventually becoming the International Code of Nomenclature for algae, fungi, and plants.

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The Code is amended at an International Botanical Congress (IBC), which is usually held every six years. The current, 18th edition, the Madrid Code, was published on 21 July 2025 and results from the 20th IBC held in Madrid in July 2024. It supersedes the Shenzhen Code of 2018.

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Madrid Code – print, epub, or PDF copies are available from The University of Chicago Press – enter the promo code UCPNEW for a 30% discount.

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The Appendices of the Code provide a permanent record of certain nomenclatural acts: conserved, protected, and rejected names, suppressed works, and binding decisions. They are available as an online searchable database.

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Provisions of the Code relating solely to names of organisms treated as fungi comprise its Chapter F, which is amended at the International Mycological Congress (IMC), usually held every four years. The current Maastricht Chapter F is included in the Madrid Code and results from the 12th IMC, which was held in Maastricht in August 2024. It supersedes the San Juan Chapter F of 2019.

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Read about the Madrid Code's new rules and recommendations for naming algae, fungi, and plants in this commentary.