The 21-year-old has been capped once in a friendly against Mexico in May 2017.
A towering centre-half born in Ljubuški, Katić started his football career at HNK Stolac in Bosnia and Herzegovina before moving to Neretvanac in Opuzen, Croatia, in 2014.
Despite his youth, Katic shone as a leader for Belupo last season as they finished seventh in the league, captaining the team for several games throughout the campaign.
Steven Gerrard has only officially been in the job a few days, yet has now sealed the club's fifth signing of the summer.
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"When they told me Steven Gerrard wanted to take me, I told my agent I'd get my shoes on and run to Scotland". He is a legend of football all over the world and I am glad to be here with him.
Gers have already signed goalkeeper Allan McGregor as well as midfielders Scott Arfield and Ovie Ejaria.
'There are a lot of long balls and duels, that's what I like'.
Brighton defender Connor Goldson is also expected to arrive in Glasgow this week to complete a £3million switch.
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"I've seen the stadium on television and I have read about the fans and the rivalry with Celtic".
"Rangers needs to be in with the top European clubs, and I will try with the other players to move this club to the top of European football".
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