Knockaert struck after half an hour and an hour at the John Smith's Stadium as Leicester, dominant throughout in west Yorkshire, won four on the spin for the first time since February 2011.
After victory at Middlesbrough on Saturday, it was also the first time the Foxes had won successive away league matches since Nigel Pearson's return as manager 11 months ago.
For Huddersfield, it was back-to-back home defeats in the league for the first time since September 2008 and they fell out of the top six.
With on-loan striker Jermaine Beckford ineligible against his parent club, Town manager Simon Grayson made one enforced change to the team that began Saturday's loss to Watford.
Sean Scannell came in for his first start since suffering a hamstring injury towards the end of August.
Leicester were also forced into a change, with Ritchie De Laet nursing a knock from the weekend.
Highly-rated teenager Liam Moore replaced the former Manchester United trainee at full-back.
Pearson made two other changes in midfield with Andy King and Lloyd Dyer getting the nod ahead of Matty James and Ben Marshall.
The Foxes started well with Knockaert and Moore looking lively down the right. But experienced centre-half Peter Clarke, making his 450th career appearance, dealt with their early crosses into the box.
David Nugent narrowly missed with a long-range shot before his strike partner Jamie Vardy saw his effort from inside the area pushed away by Huddersfield goalkeeper Alex Smithies.
Moore repelled a couple of free-kicks as the hosts attempted to get a foothold in the game.
But just as they looked like they might, Knockaert let fly from 35 yards out and beat Smithies with an absolute screamer.
King came close to making it 2-0 just before half-time after Vardy headed the ball into his path but the Wales international's 12-yard effort went just wide.
Knockaert did make it 2-0 on the hour mark.
Paul Konchesky crossed from the left and the Frenchman produced another superb finish, this time from much closer in.
Grayson responded immediately with a triple substitution, replacing Adam Clayton, Oliver Norwood and Paul Dixon with Alan Lee, Scott Arfield and Anton Robinson.
Arfield almost made an instant impact, slipping and allowing Nugent a shot on goal - but to his relief the striker's effort went wide.
Huddersfield had a sustained spell of pressure midway through the second half but Moore always seemed to be in their way, blocking shots and heading crosses clear.
Leicester nearly got a third goal in the final minute but Smithies denied Nugent from point-blank range with an excellent block.