The project announced by Stephen Hawking and Yuri Milner in 2016 to send probes to Alpha Centauri was Breakthrough Starshot.
Announced on April 12, 2016, Starshot is part of the Breakthrough Initiatives. Its proposed spacecraft would use gram-scale probes attached to ultrathin lightsails, pushed by powerful ground-based lasers rather than conventional rocket fuel.
The project aims to reach roughly 20% of the speed of light, potentially making a flyby of the Alpha Centauri system within a generation. Alpha Centauri is about 4.37 light-years from Earth and includes Proxima Centauri, the nearest known star to the Sun.
A common mix-up is Breakthrough Listen, another Milner-backed initiative announced in 2015 that searches for signals from intelligent extraterrestrial life. Project Daedalus was an earlier British interstellar-probe study, not Hawking and Milner's 2016 project.