The garden tiger moth or great tiger moth (Arctia caja) is a moth of the family Erebidae. Arctia caja is a northern species found in the US, Canada, and Europe. The moth prefers cold climates with temperate seasonality, as the larvae overwinter, and preferentially chooses host plants that produce pyrrolizidine alkaloids. However, garden tiger moths are generalists, and will pick many different plants to use as larval host plants.

The conspicuous patterns on its wings serve as a warning to predators because the moth's body fluids are poisonous. Their effects are not yet fully known, but these toxins contain quantities of neurotoxic choline esters which act by interfering with the acetylcholine receptor. The colours are also ideal for frightening predators such as small birds—the moth normally hides its hindwings under the cryptic forewings when resting. Between stored toxins, conspicuous warning coloration, and sound cues that are generated mostly as a response to bats, A. caja clearly presents itself as an inedible target for predators.

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