Lopezia guerrerensis is described as a new species for the flora of the state of Guerrero, Mexico. It is similar to the species of the Lopezia miniata complex, but is distinguished from them by its habit (subshrubs or shrubs to 3.5 m tall), whorled leaves (three per node) with brochidodromous venation and 12–14 (–17) secondary veins per side, flowers with larger lower petals and a longer fertile stamen, and inflorescences in corymbiform racemes, these axillary or grouped together in terminal panicles. For section Lopezia and the tribe Lopeziae, two new characters are added: whorled leaves (three per node) and whorled inflorescences.
