Ainsworth won only five of his 28 games in charge, and the R’s have now lost six consecutive matches including Saturday’s defeat by Leicester.
Assistant boss Richard Dobson also leaves Rangers, with the club 22nd and with just eight points from 14 games.
“Making a call such as this is never easy, and it is even more difficult when you have such respect on both a personal and professional level for the individuals concerned – which we all do for Gareth and Richard,” chief executive Lee Hoos said.
“Many supporters have told me in recent months that they have never wanted someone to succeed more than Gareth, which is an indication of the fondness everyone associated with QPR has for him.
Asked by BBC Radio London after Saturday’s defeat by the Foxes whether he expected to still be in charge despite another loss, Ainsworth said: “I can hold my head up high whether I’m here next week or not, saying I’ve given absolutely everything every single day.
“I’m proud to be the manager of this fantastic football club but at the moment we are up against some really good teams, the club has changed over the years and hopefully there’s some understanding in the fans.
“If not, no worries. I can always hold my head up high and say I’ve given everything I could for this club and done the best I possibly could.”
QPR’s form at home has been particularly poor, having gone 11 Championship matches without a win in front of their own fans – a run stretching back to last season and including nine losses.
Yet their woes at Loftus Road predate Ainsworth’s arrival, with just one victory in 22 games on home soil in all competitions since the start of November 2022.
