Young replaced Chris McCart in the role in 2008 and twice had spells as caretaker manager.
Motherwell chief executive Leeann Dempster said: "We would like to put on record our acknowledgement and thanks to Gordon for all his hard work in the last five years, particularly his two stints as interim manager of the first team.
"We are obviously sad to see Gordon go, however this is a new chapter in his career and also an exciting opportunity for the club to appoint a successor.
"I plan to meet with a few candidates over the course of the next 10 days or so."
- Sports & Recreation