Craig Brewster has been confirmed as the new manager of Dundee United.
Brewster, 39, and his assistant Malky Thomson will take charge of United after Sunday's home game with Falkirk.
A joint statement from the clubs said: "A compensation package has been fully agreed and Craig Brewster has joined United with immediate effect."
Brewster added: "It's very difficult to walk away but I've been given an opportunity that I feel is right for me at this moment."
Brewster, who was named the SPL manager of the month on Wednesday, following a nine-game unbeaten run in the league, had been at Inverness for just over a year and he leaves the club seventh in the league, with United ninth.
"League positions never lie and although Dundee United, on their day, have put in tremendous performances, the consistency hasn't been there and that's what I'm looking to put right," he added.
"I've got to believe in my own ability as a manager. I wouldn't have been given the opportunity if myself and the players hadn't done a good job and I'm looking forward to it.
"It's a massive challenge, but I'm setting no targets other than to get the best out of the players. I'm looking for better performance levels, and if we get that, we'll get results."
Brewster has been a regular player for Inverness this season and will be eligible to play for United, but asked if he planned to do so he said: "We'll have to see what happens."
Caley Thistle first-team coaches Charlie Christie and John Docherty will take charge of the team for Saturday's home game with Livingston following Brewster's departure.
Chairman David Sutherland said: "We tried our best to keep Craig but his heart was set on Tannadice and we respect that.
"He has behaved with integrity throughout and we wish him well.
"We're pleased that compensation negotiations have ended satisfactorily and we will turn our thoughts to finding a successor.
"Charlie and John will be in charge on Saturday and for Monday's cup replay at Ayr."
It was understood that Inverness had been holding out for £250,000 in compensation, but it is unclear exactly what figure the clubs settled upon.
The former Tannadice striker signed a two-and-a-half year contract when he took over from Hearts-bound John Robertson in November 2004.
He led Caley Thistle to an eighth-place finish in their first season in Scotland's top flight.
Meanwhile, Robertson has admitted that he would be interested in returning to Caledonian Stadium.