Darwin was a suggested ESA Cornerstone mission which would have involved a constellation of four to nine spacecraft designed to directly detect Earth-like planets orbiting nearby stars and search for evidence of life on these planets. The most recent design envisaged three free-flying space telescopes, each three to four metres in diameter, flying in formation as an astronomical interferometer. These telescopes were to redirect light from distant stars and planets to a fourth spacecraft, which would have contained the beam combiner, spectrometers, and cameras for the interferometer array, and which would have also acted as a communications hub. There was also an earlier design, called the "Robin Laurance configuration," which included six 1.5 metre telescopes, a beam combiner spacecraft, and a separate power and communications spacecraft.

The study of this proposed mission ended in 2007 with no further activities planned. To produce an image, the telescopes would have had to operate in formation with distances between the telescopes controlled to within a few micrometres, and the distance between the telescopes and receiver controlled to within about one nanometre. Several more detailed studies would have been needed to determine whether technology capable of such precision is actually feasible.