Mammillaria mercadensis is a species of flowering plant in the cactus family (Cactaceae), native to north and west Mexico.
The species was first described by Carlos Patoni in 1910. It has attracted a large number of synonyms.
Mammillaria mercadensis is native to the northern and western Mexican states of Michoacán, Durango, Sinaloa, Jalisco, Aguascalientes, and San Luis Potosí. It grows among volcanic rocks in desert or semi-desert habitats such as dry shrubland at elevations of .
Mammillaria mercadensis has been assessed as "least concern" by the International Union for Conservation of Nature in 2017. Some species regarded as synonymous with Mammillaria mercadensis by Plants of the World Online have been assessed differently. Mammillaria berkiana was assessed as "vulnerable" in 2009.[1] Mammillaria rettigiana was assessed as "endangered" in 2009.[2] Mammillaria guillauminiana was treated as "data deficient" in 2013, partly because of uncertainty as to its relationship with Mammillaria mercadensis.[3]