After leaving Leicester to move to the Lancashire club he will take charge of the struggling side for the first time on Sunday when they face Aston Villa at home.
Megson, 48, arrives at Bolton after a six-week stint at Championship side Leicester.
Gartside is convinced Megson has the credentials to take Bolton away from the bottom of the league.
He said: "We have been able to interview a number of quality candidates and after due consideration decided to offer the post to Gary Megson.
"I have paid particular attention to his career and he has demonstrated to me he is prepared to roll his sleeves up.
"He has the right temperament for a battle, which this season is undoubtedly going to be.''