Which plant produces the world's largest single flower?

The plant that produces the world's largest single flower is Rafflesia arnoldii. Its flower can reach about 1 metre across and weigh up to 11 kilograms, making it enormous compared with ordinary flowering plants.

Rafflesia arnoldii is a parasitic plant native to the rainforests of Sumatra and Borneo. It has no visible leaves, stems, roots, or chlorophyll. Instead, most of the plant lives hidden inside a Tetrastigma vine, drawing water and nutrients from its host.

The flower is reddish-brown with pale spots and smells like rotting flesh. That odor attracts carrion flies, which pollinate the flowers. Rafflesia flowers are either male or female, so successful reproduction requires visits to both types.

A common mix-up is Amorphophallus titanum, also called titan arum. It produces the world's largest unbranched inflorescence, which is a cluster of many tiny flowers—not one individual flower. Rafflesia's record refers specifically to a single flower.