popular has 2 distinct synonyms spread across 2 of its 4 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 unpopular.
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.
regarded with great favor, approval, or affection especially by the general public
“a popular tourist attraction”
representing or appealing to or adapted for the benefit of the people at large
“democratic art forms”
(of music or art) new and of general appeal (especially among young people)
1 of the 4 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 popular.
Synonyms, antonyms and the broader and narrower relations for popular come from Princeton University’s WordNet. Full sources and licences.