BURNLEY opened up a five-point gap in second place thanks to a first-half wonder goal from David Jones and second half strike from Dean Marney.
And this huge win in the promotion race means that by the time the Clarets host Leeds United on March 15, they will have gone a calendar year without a home league defeat.
Derby were left to play the second half win 10 men after Chris Martin was sent off for a second bookable offence just before the break.
Rams boss Steve McClaren contested the decision at half-time, after Martin appeared to be caught by Kieran Trippier in the box.
The striker had earlier been booked for catching Trippier in the face with a swinging arm.
And referee Robert Madley was quick to make such a bold decision in reducing Derby to 10 men after Martin went down theatrically in the box.
Jeff Hendrick put the ball in the net, but Madley had already blown his whistle for the Martin incident.
Burnley had already taken the lead by that point, with Jones scoring his first league goal in some style.
The flick from Danny Ings was special, but the finish from Jones - a chest down and dipping volley over former Clarets goalkeeper Lee Grant - was a contender for goal of the season.
Goalkeeper Tom Heaton was forced into a couple of saves in the second half - the best from Connor Sammon after the substitute's shot took a wicked deflection off Jason Shackell.
But there was no way back for third placed Derby once Marney doubled Burnley's lead in the 68th minute.
Jones' corner was well struck by Ings just outside the box, but two deflections took it into the path of Marney, who finished from close range.