Isoplexis is a section of four species of flowering plants within the genus Digitalis in the plantain family Plantaginaceae.

Two Isoplexis species, D. canariensis and D. sceptrum, were first described by Carl Linnaeus in 1753 as part of the genus Digitalis.

The position of Isoplexis as a section within Digitalis was finally proven by Carvalho in 1999 using molecular data and published by Brauchler et al. in 2004.

It was once thought that the original pollinators of Isoplexis and the other Canarian bird pollinated plants (such as members of the genera Canarina and Lotus) were sunbirds which had become extinct on the Canary Islands; this might explain why Isoplexis species are rare and considered endangered species (Vogel 1954; Vogel et al. 1984; Valido et al. 2004).

However more recent work has shown that these plants are adequately pollinated by non-specialist flower visiting birds, particularly the Canary Islands chiffchaff (Phylloscopus canariensis), and the Canary Sardinian warbler (Sylvia melanocephala leucogastre) (Olesen 1985, Ollerton et al. 2008), and in fact show some specific adaptations to infrequent pollination by these birds, such as extended flower lifespans (Ollerton et al. 2008), and a hexose-dominated sugar ratio in the composition of the nectar (Dupont et al. 2004).