Invasive alien species are plants, animals, pathogens, and other organisms that are non-native to an ecosystem, which may cause economic or environmental harm or adversely affect human health. In particular, they impact biodiversity adversely, including decline or elimination of native species - through competition, predation, or transmission of pathogens and the disruption of local ecosystems and ecosystem functions.

According to the Convention of Biological Diversity (CBD), alien species refers to a species, subspecies, or lower taxon, introduced outside its natural past or present distribution. Alien species include gametes, seeds, eggs, or propagules of such species that might survive and subsequently reproduce. Invasive alien species means an alien species whose introduction and spread threaten biological diversity. They produce rapidly, out-compete native species for food, water, and space, and are among the leading causes of global biodiversity loss. Species are often introduced deliberately, through, for example, fish farming, pet trade, horticulture, biocontrol, or unintentionally, through such means as land and water transportation, travel, and scientific research.

A globalised economy has resulted in increased transportation of goods, services and people which in turn facilitates the movement of live specimens over large distances, beyond national boundaries. While only a small percentage of transported organisms become invasive, those which do have a tremendous impact on the health of native biodiversity. IAS may also threaten human lives, affect local food security and ecosystem health. The presence of IAS have negatively impacted the economy of many countries anually, through loss in agricultural production and environmental remedial measures.