WTF! NAS OWES UNCLE SAM MORE THAN $2.5 MILLION!

Kelis isn't the only person trying to get money from Nas -- turns out Uncle Sam is too!
TMZ has obtained a federal tax lien filed last month against Nas for a whopping $2,584,206.31. Looks like Nas didn't pay his taxes in 2006 and 2007.

Nas is currently involved in a bitter divorce battle with Kelis. Looks like she'll have to wait in line.