Michel Adanson (7 April 1727 – 3 August 1806) was a French naturalist of Scottish descent.

Adanson was born at Aix-en-Provence. His family moved to Paris in 1730. After leaving the College Sainte Barbe he was employed in the cabinets of R.A.F. Reaumur and Bernard de Jussieu, as well as in the Jardin des Plantes. At the end of 1748 he left France on an exploring expedition to Senegal. He remained there for five years, collecting and describing numerous animals and plants. He also collected specimens of every object of commerce, delineated maps of the country, made systematic meteorological and astronomical observations, and prepared grammars and dictionaries of the languages spoken on the banks of the Senegal.

After his return to Paris in 1754 he made use of a small portion of the materials he had collected in his Histoire naturelle du Senegal (1757). This work has a special interest particularly for the essay on shells, printed at the end of it, where Adanson proposed his universal method, a system of classification distinct from those of Buffon and Linnaeus. He founded his classification of all organized beings on the consideration of each individual organ. As each organ gave birth to new relations, so he established a corresponding number of arbitrary arrangements. Those beings possessing the greatest number of similar organs were classified into one great division, and the relationship was considered more remote in proportion to the dissimilarity of organs.

In 1763 he published his Familles naturelles des plantes. In this work he developed the aforementioned principle of arrangement, which, in its adherence to natural botanical relations, was based on the system of Joseph Pitton de Tournefort, and had been anticipated to some extent nearly a century before by John Ray. The success of this work was hindered by its innovations in the use of terms, which were ridiculed by the defenders of the popular sexual system of Linnaeus; but it did much to open the way for the establishment, by means principally of Antoine Laurent de Jussieu's Genera Plantarum (1789), of the natural method of the classification of plants.

In 1774 Adanson submitted to the consideration of the French Academy of Sciences an immense work, extending to all known beings and substances. It consisted of 27 large volumes of manuscript, employed in displaying the general relations of all these matters, and their distribution; 150 volumes more, occupied with the alphabetical arrangement of 40,000 species; a vocabulary, containing 200,000 words, with their explanations; and a number of detached memoirs, 40,000 figures and 30,000 specimens of the three kingdoms of nature. The committee to which the inspection of this enormous mass was entrusted strongly recommended Adanson to separate and publish all that was peculiarly his own, leaving out what was merely compilation. He obstinately rejected this advice; and the huge work, at which he continued to labour, was never published.

He had been elected a member of the Academy of Sciences in 1759, and he latterly subsisted on a small pension it had conferred on him. Of this he was deprived in the dissolution of the Academy by the Constituent Assembly, and was consequently reduced to such a depth of poverty as to be unable to appear before the French Institute when it invited him to take his place among its members. (It is said that he possessed neither a white shirt, a coat nor a whole pair of breeches.) Afterwards he was granted a pension sufficient to relieve his simple wants.

He died at Paris after months of severe suffering, requesting, as the only decoration of his grave, a garland of flowers gathered from the fifty-eight families he had differentiated - "a touching though transitory image," says Georges Cuvier, "of the more durable monument which he has erected to himself in his works."

Besides the books already mentioned he published papers on the ship-worm, the baobab tree (whose generic name Adansonia commemorates Adanson), the origin of the varieties of cultivated plants, and gum-producing trees.

His papers and herbarium remained in his family's hands for over a century and a half, finally coming to the Hunt Botanical Library around 1960. Subsequently the Hunt Institute republished his Familles des plantes in two volumes (1963-64), under the editorship of G.H.M. Lawrence.