"Glenn was here for a long time and did a tremendous job," Haag said.
"I hope I can be here for nearly as long and take things the next step. We are not at a stage where we will be promoted next week, but we have a great opportunity to push for the top four where the board wants us to be.
Haag was born on 28 July, 1968.
He played 315 games for Bath and won full two caps for England - against Argentina in 1997.
Haag was Bristol forwards coach until 2007 in which time he helped the side win promotion and finish third in the Premiership.
He had two spells as Bath Academy coach.
Helped the England Under-20 side to the final of the 2008-09 World Championship as assistant coach before taking appointment at Bath.
Worked with the RFU Academy until taking Premiership role with Bath.
His appointment at Nottingham is his first head-coach role.
"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."
Chairman Alistair Bow said Haag's knowledge of the game, from youth development to the highest levels of the sport, makes him an exciting choice.
"This is an important appointment for the board to make and one that we are very proud to announce," Bow said.
"Martin's knowledge of the Championship, demands of the Premiership and academy coaching background, really fits the criteria of what we were looking for.
"This in an ambitious club and Martin is an ambitious coach who wants to get us to the Premiership. As a board we don't expect miracles, but we know he is going to give it a great go."
Ben Johnston, Neil Fowkes and Jo Brun will all remain part of the coaching set-up under Haag.
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