* obediente - obedient
* obedecer - to obey
* obeso - obese
* objetivo - objective
* objeto - object
* obligatorio - obligatory
* obra - work
* obrero - worker
* observar - to observe
* obtener - to obtain
* obvio - obvious
* ocasión - occasion
* occidental - western
* océano - ocean
* ochenta - eighty
* ocho - eight
* ocioso - idle
* ocultar - to hide
* ocurrir - to happen
* odiar - to hate
* odio - hatred
* odontología - dentistry
* oeste - west
* ofender - to offend
* ofensa - offense
* oferta - offer
* ofrecer - to offer
* oficina - office
* oficial - official
* oficio - office
* oído - ear
* oír - to hear
* ojala - hopefully
* ojo - eye
* ola - wave
* oler - to smell
* olvidar - to forget
* olímpico - olympic
* ombligo - navel
* omega - omega
* ominoso - ominous
* omisión - omission
* omitir - to omit
* omnipotente - omnipotent
* ómnibus - bus