Diplacus is a genus of flowering plants in the family Phrymaceae, which was traditionally placed in family Scrophulariaceae. It includes 49 species native to the western United States and northwestern Mexico. Most prefer dry and rocky areas.

The genus Diplacus was first described by Thomas Nuttall in 1838. It was merged into Mimulus no later than 1905, until the 2012 restructuring. The 2012 restructuring of Mimulus by Barker, et al., based largely upon DNA evidence, left seven species in Mimulus, placed 111 into Erythranthe (species with axile placentation and long pedicels), placed 46 into Diplacus (species with parietal placentation and sessile flowers), placed two in Uvedalia, and placed one each in Elacholoma, Mimetanthe, and Thyridia.

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