The 6ft 3in striker rejected an offer from relegated Caley Thistle after scoring six goals in their final eight league games, four of them coming against his new employers. The 26-year-old scored eight goals in all last season.
The former Oxford, Mansfield and Torquay forward has also had spells in Spain, Belgium and Italy, and Motherwell say they fended off competition from Premiership rivals as well as Sky Bet League One clubs to sign him on a two-year contract.
Fisher, who is Stephen Robinson’s first signing, told Motherwell’s YouTube channel: “It’s fantastic. I spoke to the gaffer at the end of the season, had a good talk and I’m delighted to get this move over the line.
“It’s a big club with a great fan base and good history. And when I spoke to the manager and he told me about his plans for this season, I knew I wanted to be a part of it so it was an easy decision.”
Motherwell quickly added a second signing by bringing in former Rangers loanee Gael Bigirimana.
The 23-year-old Burundi midfielder has signed a two-year contract after deciding to leave Coventry.
The former Newcastle player, who did not play for Rangers during his spell at Ibrox because of illness, said: “I’m very excited and first of all I thank God for this. I know Motherwell has a great history and I look forward to pulling on the top.”
Robinson added: “Gaal is a super signing for us, he gives us something we’ve been missing in midfield and comes with a great pedigree, having played at a very good level.
“His desire to come and play for Motherwell and to the Scottish Premiership sold him to me just as much as his ability - Gael is a real coup for Motherwell.”