Alan Solomons has stepped down as Edinburgh boss, with assistant Duncan Hodge appointed acting head coach.
South African Solomons, 66, took over from Michael Bradley at Murrayfield in 2013 and led the side to the 2015 European Rugby Challenge Cup final.
But their Pro12 campaigns have been disappointing - two eighth-place finishes followed by ninth last season.
Solomons believes he is leaving the club "in a better place" than when he arrived and wished Hodge well.
"I have greatly enjoyed working with the players and coaches and feel I have helped to put the club on a much stronger footing over the past three years," Solomons added.
Former Scotland and Edinburgh fly-half Hodge, 42, has been attack coach under Solomons since last November and previously held the same role with the national team.
His fellow assistants, forwards coach Stevie Scott and defence coach Peter Wilkins, will remain in their current roles.
Edinburgh's players identified a top-four finish in the Pro12 as a 'minimum criteria' this season, but they are already 10 points adrift of fourth place after three defeats in their opening four matches.
Scottish Rugby chief executive Mark Dodson said: "Alan came in as head coach at a difficult time in Edinburgh Rugby's history and helped to stabilise and strengthen the club.
"He achieved some notable successes including leading the first Scottish team to a European final of the Challenge Cup in 2015 and back-to-back 1872 Scottish Cup victories over Glasgow Warriors.
"Duncan brings his recent coaching experience from the Scotland national team as well as his long playing career with Edinburgh into the role and he will receive our full support to keep moving the club forward.
"I would like to take this opportunity to thank Alan for his significant contribution to the Edinburgh club and I wish him well for the future."
Analysis - Tom English, BBC Scotland
Alan Solomons was a lawyer by trade and adept at arguing his point in the face of consistent failure. He became a bit of an excuse-making machine, borne out of frustration at his inability to move Edinburgh forward. He ran the gamut of excuses - from a lack of conditioning among his players, to difficulties integrating so many foreign players, to injuries, to the weather, to officials making bad calls.
The case for the defence had grown tired long before his departure.
True, Edinburgh made a European Challenge Cup final on his watch but given the budget he had and the vast number of players recruited, mostly from the southern hemisphere, it was a desperately poor return.
Everybody waited for progress, but there wasn't any. Solomons was hugely committed to his job - and vastly experienced - but his team played dull, one-dimensional stuff. It was one forward-dominated grunt-athon after another. Little ambition, little joy.
They never made the top seven of the Pro12, never mind the top four. The SRU renewed his contract midway through last season when Edinburgh were sitting fifth in the Pro12. There was no need to do it. Edinburgh ended up finishing ninth.
He should have gone at that point but his employers allowed him to carry on. That was inexplicable. The SRU deserve a lot of criticism for that.