| Oscar Hammerstein II Oscar Palmer Robertson
 Oscar Robertson
 Oscar Wilde
 Oscar bait
 Oscar the Grouch
 Oscars
 Osci
 Oscillatoria princeps
 Oscillatoriaceae
 
 | Oscines Osco-Umbrian
 Osgood
 Osh
 Oshikwanyama
 Oshindonga (current term)
 Oshiwambo
 Osip Emilevich Mandelstam
 Osip Mandelstam
 Osirian
 
 | Osiris Osler
 Osler's disease
 Osler's sign
 Osler-Vaquez disease
 Osler node
 Osler nodes
 Oslo
 Osloite
 Osloites
 
 |