naive has 6 distinct synonyms spread across 4 of its 5 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. Its one recorded opposite is sophisticated.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
marked by or showing unaffected simplicity and lack of guile or worldly experience
“a teenager's naive ignorance of life”
of or created by one without formal training; simple or naive in style
“primitive art such as that by Grandma Moses is often colorful and striking”
lacking information or instruction
“lamentably unenlightened as to the laws”
not initiated; deficient in relevant experience
“it seemed a bizarre ceremony to uninitiated western eyes”
1 of the 5 recorded senses carries no synonym, antonym or related term, so it is not shown above. Every sense, with its definition and examples, is on the full entry for naive.
Synonyms, antonyms and the broader and narrower relations for naive come from Princeton University’s WordNet. Full sources and licences.