Largest genus of cactus

The largest genus of cactus is Mammillaria, commonly referred to as globe cacti or pincushion cacti, with approximately 140 recognized species among the total 1,600 or so formally recognized as of August 2023. As with all cacti, the genus is native to the Americas, with species found between Mexico (which is home to around 99% of all Mammillaria; 88% endemically) and southwards to Colombia and Venezuela, as well as in some Caribbean islands.

At one point the total number of Mammillaria species was thought to number more than 200, however a sizeable subset of these have since been reclassified into similar-looking genera such as Cochemiea after molecular phylogenetic scrutiny.

This genus's name is derived from the Latin for "nipple" in reference to the rounded tubercles that are a distinctive feature of this group of cacti. The genus was so-named by British botanist Adrian Hardy Haworth in 1812, though the first-known Mammillaria was described by the Swedish botanist Carl Linnaeus in 1753 as Cactus mammillaris.