Christopher Samba has completed a £12.5m move to QPR from Russian side Anzhi Makhachkala.
The ex-Blackburn defender, 28, has signed a four-and-a-half-year deal and it is understood he will receive £100,000-a-week, including bonuses and add-ons.
"This is an unbelievable signing," manager Harry Redknapp told the QPR website.
"Chris is just what we need. He's a monster."
Despite Samba's reported six-figure weekly wage, Redknapp said the player had taken a "massive pay cut" to move to the Premier League's bottom club,
"I've tried to sign him loads of times," added the Hoops boss on the club's official weekly phone-in show 'London Call-In'. "He was willing to take a massive pay cut because I don't think he was enjoying it over there.
"He's great in the air, quick, a leader, strong, fantastic in both boxes, hard as nails. He's a proper centre-half.
"Tony Fernandes (the chairman) deserves a lot of credit for this one - he has worked so hard on bringing him in.
"I was speaking with him a month ago and he asked me who I would want to sign if Ryan Nelsen left, he asked me to give him a couple of names.
"I said to him, 'Well, these aren't possible to get but if you're asking me who I'd have, I'll give you a couple of players'. One of them was Chris Samba.
"The next thing I know he's telling me that he's working on bringing him in! It's amazing."
Anzhi head coach Guus Hiddink admitted he was disappointed to lose Samba.
"It's not a very good situation," Hiddink told Russian newspaper Sport Express.
"Samba was with us during this season, began preparations for the winter training camps and suddenly this opportunity arose with an English club. Yesterday [Tuesday] he left for England. Unfortunately, we didn't even have a chance to say goodbye to him. Everything has developed very quickly."
Samba left England in February 2012 when Anzhi agreed to pay Blackburn £12m, amid interest from Tottenham, Redknapp's former club.
With Nelsen leaving Loftus Road to manage Toronto FC, and Anton Ferdinand moving to Turkish club Bursaspor on loan, QPR have been desperate to sign an authoritative central defender with Premier League experience.
Redknapp said plans to sign Stoke striker Peter Crouch had fallen through.
"I've signed Crouchy so many times and he's had a great career but [Potters boss] Tony Pulis decided in the end not to let him go," he said.