The Optical Gravitational Lensing Experiment (OGLE) is a Polish astronomical project based at the University of Warsaw that runs a long-term variability sky survey (1992–present).

The main goals are the detection and classification of variable stars (pulsating and eclipsing), discovery of microlensing events, dwarf novae, and studies of the structure of the Galaxy and the Magellanic Clouds.

The main targets of the experiment are the Magellanic Clouds and the Galactic Bulge, because of the large number of intervening stars that can be used for microlensing during a stellar transit.

[2] OGLE-III (2001–2009) expanded the camera to a mosaic of eight 2048×4096 pixel CCDs, and was able to search for gravitational microlensing events and transiting planets in four fields: the Galactic Bulge, the constellation Carina,[3] and toward both Magellanic Clouds.

In 2010, following engineering work in 2009, the fourth and current phase, OGLE-IV, was started using a 32-chip mosaic CCD camera which fills the Warsaw telescope's 1.5° field of view.