O. flavescens may refer to:
Obolcola flavescens, a geometer moth Oligoryzomys flavescens, a southern South American rodent Ommatius flavescens, a robber fly Onchidella flavescens, a sea slug Opistophthalmus flavescens, a burrowing scorpion Orchesella flavescens, a slender springtail Oria flavescens, an owlet moth Orthosia flavescens, an owlet moth Otaria flavescens, a sea lion Ozarba flavescens, an owlet moth