Swindon Town: Martin Ling leaves for health reasons
The 49-year-old, who was appointed on 3 November after Mark Cooper's sacking, had been in charge for just 56 days.
It was Ling's first managerial role since leaving Torquay United in April 2013, having been forced to take time out of the game because of depression.
Swindon, who won five of their nine matches under Ling, said they would release a statement in "due course".
Following his appointment at the County Ground last month, former Robins player Ling said his depression had "gone" and that he was "really excited to restart a career that was going very well".
His first taste of management came in 2003 with a five-and-a-half-year stint at Leyton Orient, prior to spells at Cambridge United and Torquay.
Ling had been at Plainmoor for 18 months before stepping away to recover from what the club described as a "debilitating illness" in January 2013 and, although he was expected to return, his contract was terminated three months later.