Delphinium is a genus of flowering plant native throughout the Northern hemisphere and in parts of Africa. It features stems covered in flowers that bloom from the late spring throughout the summer and may be blue, red, purple, yellow, or white. There are about 250 different species of delphinium in annual, biennial, and perennial varieties. Delphinium is also commonly called larkspur, lark's claw, lark's heel, and knight's spur.

The flower stalks of delphinium species vary widely in height, from 4 inches (10 cm) to 6 1/2 feet (2 meters). Delphinium flowers are hollow and five-petalled, with a spur at the end. The plant also features small, shiny, black seeds. All parts of the plant are poisonous, and eating it can cause vomiting and, in extreme cases, death.

Despite the toxicity of delphinium, it has historically been used to treat a number of medical complaints, usually in extract form. Some conditions that have been treated with delphinium are insect bites, parasitic infestation, dropsy, and asthma. It was also historically used for eye complaints and is associated with Saint Odile, the patron saint of eye and ear diseases.

Delphinium is quite popular as a garden plant for its lovely, abundant blooms. Many cultivars have been specifically developed for the garden with thickly clustered, prominent flowers. The juice of delphinium flowers can also be made into a blue ink by mixing it with alum.

Two species of delphinium native to California, Yellow Larkspur and Baker's Larkspur, are critically endangered and the focus of conservation efforts. Road crews devastated Baker's Larkspur populations in the first years of the 21st century, and only 35 members of the species are currently known to exist. There are thought to be less than 100 Yellow Larkspur individuals.

Grazing cattle in the western United States are often poisoned by naturally growing delphinium. Because the plants are less dangerous when not in bloom, ranchers often confine cattle to lower elevation ranges, where delphinium does not grow, during the spring and summer months.