The former England manager joined the Loftus Road club last summer but has been sacked with the club 17th in the Championship table and only eight points clear of the relegation zone.
QPR director of football Les Ferdinand said in a statement: "Steve has worked incredibly hard during his time with us but as we start to make plans for next year we feel this change is necessary now, rather than wait until the end of the season, or risk having to make such a decision early in the new campaign."
McLaren was in charge of the club for 46 matches in all competitions, winning 16 and losing 21.
Chief executive Lee Hoos added: "Making a decision such as this is never easy, particularly when you are talking about someone as professional and dedicated as Steve.
"We are grateful to him for all his efforts during his time with us. It is well documented that we are in a period of transition as we work hard to make the club financially stable. With that comes challenges, not least the cutting of the wage bill while aiming to remain competitive.
"As we look to the future, and taking recent results into account, we feel now is the right time to re-evaluate where we are."
The club have confirmed that assistant manager John Eustace will take over first-team affairs on an interim basis.
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