Brunfelsia is a genus of about 50 species of neotropical shrubs and small trees.

The leaves are alternate and simple, with shapes generally elliptic to ovate. The flowers are large and tubular, with five broad petals. Typical habitat is light woodland and thickets. Species in cultivation include Brunfelsia americana ("lady of the night") and Brunfelsia pauciflora. Linnaeus named the genus for early German herbalist Otto Brunfels (1488–1534). The cultivated plant is commonly called "yesterday, today, and tomorrow" due to its color changes.

Many members of this genus contain toxic and medicinal alkaloids. Brunfelsia grandiflora is used by curanderos in South America as an additive to ayahuasca and contains the psychoactive chemical scopoletin. Scopoletin has no N atoms and is not an alkaloid. Brunfelsia hopeana contains the alkaloid hopeanine.

Brunfelsia has always been placed in the family Solanaceae, where it is a member of the tribe Petunieae, the same group that also includes Petunia. This placement is also supported by molecular data ^[1].