Ronald Araujo will wear the no.33 shirt at Liverpool after he joined from Barcelona on a season-long loan.
The agreement between both clubs for the 27-year-old has an option to buy.
Araujo arrived in Merseyside on Sunday afternoon and has completed his medical tests.
He said: “I think it was the ideal move for me at this stage in my career. I think it was a move that was necessary for me to take.
“As soon as I heard that interest from Liverpool, everything went into action really, really quickly.”
Araujo leaves Barcelona after eight years, having been told by manager Hansi Flick that he could not guarantee him enough playing time this season.
He will provide cover in Liverpool’s defence, after Joe Gomez suffered a muscle injury in a preseason game.
Teenage centre-back Giovanni Leoni is still recovering from an ACL injury, while new signing Jeremy Jacquet has not played for the Reds.