Haag, who won two caps for England during his playing career, was part of the Bath coaching staff for three seasons, but he followed Sir Ian McGeechan out of the club following a disappointing campaign last term.
He succeeds Glenn Delaney, who has joined the coaching staff at London Irish, as head coach of the Green and Whites.
Haag is looking forward to getting down to work at a club with top-flight aspirations.
"The opportunity to be a head coach was a big driver for me and this is a very exciting club to be a part of," Haag said.
"Having done my homework and gone through the interview process I've been impressed by the board, their ambition and how they see the club in the future, and not just talking about the next year, but long term.
"When I first came in to meet the board, looked at the home ground Meadow Lane, toured the training facility at Lady Bay, I could see that this would be a fantastic place to be. There is incredible infrastructure here, we just have to build on it."
Gilbert has released a new line of rugby cleats. The Gilbert Virtuo 8S is part of the exciting new product. Check it out.
The entire All Blacks apparel line has been updated for 2013/14. Check out the New Zealand All Blacks polo.
The Nike Tiempo is a solid rugby cleat and one of few styles still made from full-grain natural leather.
The Gilbert Blitz 8S rugby cleat is a great cleat at a great price of $69.99. Get a new pair of cleats today.
A cool looking all black rugby cleat with the high performance adidas is known for. Get in the Gear!
Wear the crest of the British and Irish Lions on your t-shirt. A great look for the summer.
The All Blacks Performance t-shirt is black with hints of blue from the training jersey. Very Cool.
The New Zealand All Blacks training jersey for 2013/14. Get in the Gear!
The USA Rugby Pro Alternate rugby jersey is perfect for any fan of the Eagles. Get yours to wear during the summer Test matches.
The NEW All Blacks 2013/14 jersey has arrived at World Rugby Shop. Dare to wear the colors of the All Blacks.