Justicia is a genus of flowering plants in the family Acanthaceae. There are 658 species with a further 611 species as yet unresolved by Kew. They are native to tropical to warm temperate regions of the Americas, India and Africa. Common names include water-willow and shrimp plant, the latter from the inflorescences, which resemble a shrimp in some species. The generic name honours Scottish horticulturist James Justice (1698–1763). They are closely related to Pachystachys.