Paul Anka -- one of the greatest singer/songwriters of all time -- is calling out Jay-Z ... telling TMZ the rapper treated him like a chump ... and now Anka is PISSED.
Anka was outside Madeo restaurant in L.A. last night, when we asked about his upcoming album "Duets" -- which features collaborations with legends like Willie Nelson, Gloria Estefan and Dolly Parton.
But you know who isn't on the album? Jigga ... because according to Anka, Mr. Knowles didn't have the common courtesy to return a simple phone call!!!
Now, Anka is escalating his anger into a full on war of the music titans -- and even took a shot back at Jay-Z.
Not many people in the music biz would have the stones to go after Hova ... then again, not many people would have the stones to disrespect Anka either.