Solanaceae (), commonly known as the nightshades, is a family of flowering plants in the order Solanales. The family contains approximately 2,700 species, several of which are used as agricultural crops, medicinal plants, and ornamental plants. Many members of the family have high alkaloid contents, making some highly toxic, but many—such as tomatoes, potatoes, eggplants, and peppers—are commonly used in food around the world.

Originating in South America, Solanaceae now inhabit every continent on Earth except Antarctica. After the K–Pg extinction event they rapidly diversified and have adapted to live in deserts, tundras, rainforests, plains, and highlands, and taken on wide range of forms including trees, vines, shrubs, and epiphytes. Nearly 80% of all nightshades are included in the subfamily Solanoideae, most of which are members of the type genus Solanum. Most taxonomists recognize six other subfamilies: Cestroideae, Goetzeoideae, Nicotianoideae, Petunioideae, Schizanthoideae, and Schwenkioideae, although nightshade taxonomy is still controversial. The genus Duckeodendron is sometimes placed in its own subfamily, Duckeodendroideae.

The high alkaloid content in some species has made them valuable for recreational, medicinal, and culinary use. The tobacco plant has been used for centuries as a recreational drug because of its high nicotine content. The tropanes in Atropa bella-donna can have pain-killing, relaxing, or psychedelic effects, making it a popular plant in alternative medicine, as well as one of the most toxic plants in the world. The presence of capsaicin in Capsicum species gives their fruits their signature pungency, which are used to make most spicy food products sold today.

Other nightshades are known for their beauty, such as the long, slender flowers of Brugmansia, the various colors of Petunia, or the spotted and speckled varieties of Schizanthus.

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