Mainz have signed Giulio Donati from Bayer Leverkusen on a three-and-a-half-year contract for an undisclosed fee.
Gonzalo Jara's departure to Universidad de Chile this month put Mainz in the market for a defender and they have moved for Donati, tying him to the club until June 2019.
The 25-year-old made 12 Bundesliga appearances for Leverkusen this season and started four of their Champions League group-stage fixtures.
Donati trained with his new team-mates on Monday and could be used in Friday's meeting with Borussia Monchengladbach.
"After the departure of Gonzalo Jara we were looking for a reinforcement of our squad in the full-back position and we have found it in Giulio Donati," manager Christian Heidel said in a club statement.
"He has already proven himself in the Bundesliga with a top team. We are pleased to have a good, passionate footballer and fine character that enhances our squad."