Manninger, who has previously turned out for Arsenal, Siena and Juventus among others in a 21-year senior career, has signed a one-year deal.
The veteran had been on trial with Klopp’s squad since the second week of July, and has sufficiently impressed the Reds manager, earning a spot in his first-team squad.
He will also add considerable experience on the training ground, with 23-year-old Karius no doubt benefiting from his influence at Melwood.
Liverpool have already sanctioned the loan departures of Adam Bogdan, Danny Ward and Ryan Fulton this summer, with the trio joining Wigan Athletic, Huddersfield Town and Chesterfield Town.
Manninger has joined Klopp’s squad for their pre-season tour of the US, along with Karius and 18-year-old academy stopper Shamal George.
Mignolet is due to join up with his team-mates on Friday, after his summer exploits with Belgium at the European Championship.
Klopp has now made five signings so far this summer, with Manninger joining Karius, Joel Matip, Ragnar Klavan and Sadio Mane, while Marko Grujic has arrived following a loan spell with Red Star Belgrade.
Klopp has been keen to finalise his squad early in the summer, and a move to sign Manninger as his third-choice goalkeeper has ensured this is one step closer.