Benitez scooped the award after Liverpool beat Bolton 3-0, Watford 3-0, Chelsea 2-0 and West Ham 2-1 last month.
"It's been a very happy new year for the red half of Merseyside," said Jim Hytner of the Barclays Awards Panel.
"Undefeated and just one goal conceded in the Premiership this year, Benitez has revitalised Liverpool's campaign."
