The former Newcastle, Sunderland and Fulham midfielder Clark has left Norwich where he was the assistant boss to Glen Roeder. Huddersfield chairman-elect Dean Hoyle will formally introduce the new man on Friday morning.
Hoyle told the club website: "Some fans may worry about [Clark's] young age and his perceived lack of experience and I suppose in that sense it is a gamble. But he is exactly what I was looking for and he will be surrounded by experience. Lee played a good, quick passing style of football throughout his playing career and he will carry that into management - that is how he wants his team to play. He also wants his team to be as fit and as organised as possible."
Though caretaker Gerry Murphy, in his third spell in charge, has won three games out five, including a terrific away victory at rivals Leeds, he always made it clear the side needed a younger man.
Clark will be the club's fourth manager in the space of two years following Peter Jackson, Andy Ritchie and Stan Ternent, who was sacked in early November after only six months in charge.
Clark's backroom staff will consist of the ex-England and Newcastle coach Derek Fazackerly, as well as fitness and psychology trainer Steve Black. Fazackerly will become Clark's assistant, with Black filling the role of performance coach. The three previously worked together at Newcastle United when Clarke, 36, was a player under Kevin Keegan.
After ending his playing career, Clark later joined the coaching staff at St James' Park under Glenn Roeder, before linking up with him again at Norwich City. For Clark, who is currently completing his Uefa Pro Licence, the Hudderfield job is his first chance as a manager.
Norwich have confirmed an undisclosed compensation payment has been agreed and Roeder wished Clark well in his new post at the Galpharm Stadium: "I always knew from day one when I first appointed Lee as reserve-team coach at Newcastle how ambitious he was to become a manager one day so he goes with my best wishes and big thanks for the part he played last year in helping the club to secure its Championship status. I just want to say I truly hope Lee goes on to fulfil his ultimate ambition by one day managing Newcastle United, any Geordie's dream."