Who plays Will Hunting's psychologist and mentor in the film 'Good Will Hunting'?

Explanation

'Good Will Hunting' from 1997 became a big hit, both in artistic and commercial terms. The film was written by the two lead roles and friends, Ben Affleck and Matt Damon, and directed by cult director Gus Van Sant. Robin Williams plays Will Hunting's mentor and psychologist. The talented singer-songwriter Elliott Smith, who died in 2003, was behind most of the soundtrack. Just like Will Hunting in the film, Matt Damon also attended Harvard.