He later became the club's captain ahead of the 2014-2015 season following the retirement of Inter Milan great Javier Zanetti.
Ranocchia, who was replaced by Argentine striker Mauro Icardi as captain, has made only 10 appearances in the current Serie A season.
"I want to repay the fans, boss and club for their confidence," he told the Sampdoria website. "This is a very good group of players, who definitely deserve to be higher up the league than they are.
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"I know many of the lads and have played before with some of them, others I know from the national team. I hope to feel at home quickly and make my contribution."
Sampdoria, 17th in Serie A, play 12th-placed Bologna on Sunday.
($1 = 0.9141 euros)
(Reporting by Silvia Recchimuzzi and Anna Jaworska-Guidotti in Gdynia; Editing by Alan Baldwin and Dominic Evans)
