Luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs) dominate the star formation rate budget of the universe at z>~1, yet no local measurements of their heavy-element abundances exist. We measure nuclear or near-nuclear oxygen abundances in a sample of 100 star-forming LIRGs and ULIRGs using new, previously published, and archival spectroscopy of strong emission lines (including [OII] {lambda}{lambda}3726, 3729) in galaxies with redshifts <z>~0.1.