The 20-year-old has made just one Premier League appearance for the Red Devils during his time with the club, back in 2011.
Keane, an England U21 international, will join fellow Manchester United starlet Nick Powell, who is currently on loan at the DW Stadium, until New Year's Day.
The young striker missed the entire 2012/13 campaign with a cruciate knee ligament injury, and has scored four times since his return to action with the U21's and reserves.
The reigning Premier League champions also confirmed that Michael Keane will join Derby County until January 2.
A statement on Derby's official site read: "Derby County have this afternoon completed the signing of Manchester United central defender Michael Keane on an emergency loan deal until 2nd January 2014.
"Head of Football Operations Chris Evans has worked tirelessly during the last 24 hours to secure a deal with the Premier League Champions and the 20-year-old defender will be available for Sunday’s Sky Bet Championship game at Wigan Athletic, subject to clearance from the Football League.
"After signing England Under 21 international captain Andre Wisdom on a season-long loan from Liverpool last month, Head Coach Steve McClaren has once again moved to attract one of the country’s top talents to the Rams."
The 20-year-old has never made a Premier League appearance at Old Trafford, and spent last season on loan at Leicester City.
Manchester United currently have eight players out on loan, including Angelo Henriquez who is with Spanish outfit Real Zaragoza.