Gutwillig was a prominent figure in the LGBT film community and a driving force at the festival who instigated, among other programmes, the Outfest Legacy Project, currently the only LGBT film preservation project in existence.
Under his tenure the festival developed the Outfest Screenwriting Lab and Fusion, the nation's first LGBT people of colour film festival.
The board of directors is searching for a replacement and has promoted senior director of programming and operations Kirsten Schaffer to co-executive director, effective immediately.
Upon Gutwillig's departure, Schaffer will serve as interim executive director while the hunt for a new appointment goes on.
'Stephen's leadership has made a difference for the LGBT community far beyond our home base here in Los Angeles,' Outfest board of directors co-president Stephen Macias said.
'I am enormously proud of Outfest and all the growth and change I've been privileged to lead,' Gutwillig said. 'The premiere of our first feature film restoration, Bill Sherwood's Parting Glances, at the 25th anniversary festival in July, was the highlight of my career.
'That landmark and all of the current programmes offered by Outfest represent promises fulfilled and demonstrate the limitless potential of the organisation, making it a little easier for me to let go and allow others to guide Outfest in what looks to be an extraordinary next phase of its development.'
The formal executive director job posting will be available Nov 15, 2007.