Phillip Phillips -- FINALLY Undergoes Surgery to End Kidney Pain

Phillip Phillips finally went under the knife to remove the enormous kidney stones that almost derailed his run to the "American Idol" title ... TMZ has learned.

We're told Phillip had the 6 and a half hour long surgery in L.A. yesterday -- and he is recovering well today. The stones that were removed were so huge there was no chance he could've passed them on his own.

As TMZ first reported, Phil was scheduled to have the surgery last week ... but it was delayed because he had a fever and sinus infection.

Phillip suffered through excruciating pain during the entire season of 'Idol.' It obviously paid off.

Oh what a relief.

9:05 AM PT -- Phillip's rep says the surgery went well, adding, "He's resting and will be ready for the Idol tour kickoff in July!"