When was gravitational lensing first observed?

The first widely accepted observation of gravitational lensing was published in 1979, when astronomers found the double quasar Q0957+561. It turned out to be a single quasar whose light was bent by a foreground galaxy, creating two images. This was one of the earliest major confirmations of Einstein’s prediction from general relativity that gravity can bend light. Gravitational lensing later became a powerful tool for studying dark matter, distant galaxies, and the expansion of the universe.