French full-back Kevin Theophile-Catherine has joined Premier League side Cardiff from French Ligue 1 side Rennes for a reported £2.1m.
The 6ft defender, a seventh addition for City's first Premier League campaign, has signed a four-year deal.
Cardiff boss Malky Mackay said: "He is someone we have tracked and watched for a period of time.
"We have to make sure we have cover everywhere and that we have players who are pushing each other."
He added: "Kevin brings that from a top division in French football.
"He brings defensive strength and solidity to us."