A pest is any living organism, whether animal, plant or fungus, which is invasive or troublesome to plants or animals, human or human concerns, livestock, or human structures.

It is a loose concept, as an organism can be a pest in one setting but beneficial, domesticated or acceptable in another.

The Prevention of Damage by Pests Act 1949

The Weeds Act 1959

The Ragwort Control Act 2003