Which butterfly is considered the world's largest by wingspan?

The butterfly considered the world’s largest by wingspan is Queen Alexandra’s birdwing.

Its scientific name is Ornithoptera alexandrae, and females can reach slightly more than 25 centimetres across. Females are substantially larger than males and have broad, brown wings with pale markings; males are smaller and vividly colored, with iridescent blue-green wings and yellow on the abdomen.

The species is restricted to forests in Oro Province, eastern Papua New Guinea. It was discovered in 1906 by collector Albert Stewart Meek, and Walter Rothschild formally named it the following year in honor of Alexandra of Denmark. The first specimen was collected with a shotgun because the butterfly flew high in the forest canopy.

“Largest butterfly” usually means greatest wingspan, not greatest body mass, wing area, or individual size in every measurement. The Queen Alexandra’s birdwing is also endangered and is listed in Appendix I of CITES, which places strict controls on international commercial trade.