The 61-year-old was unveiled as the new Loftus Road chief after the club agreed a compensation package with Championship rivals Crystal Palace.
Warnock’s future had become uncertain at Selhurst Park after the club went into administration in January.
And now the ex-Sheffield United chief, inset, becomes Rangers’ fifth manager of the season, replacing caretaker Mick Harford.
“I am delighted to be joining a club with the history that QPR has,” Warnock said. “As a manager, Loftus Road is always a place I loved because of the fantastic atmosphere there.
“Looking from afar I believe this is the perfect time for me to come in, with the new structure and chairman in place. Together we can give the club the stability that it needs. I am really looking forward to the challenge that’s in front of me.”
QPR chairman Ishan Saksena insisted Warnock was always the club’s No1 target.
He added: “He has great experience in English football and a phenomenal track record. I believe he is the right man to help QPR achieve its ambitions.”
Warnock leaves Palace in the thick of a relegation battle following their ten-point deduction for going into administration, while Rangers lie one place and three points ahead in the table.