Yes, Halloween is considered a proper noun. Proper nouns are specific names that identify a particular person, place, or thing, and in this case, Halloween refers to a specific holiday celebrated on October 31st each year.
Proper nouns are typically capitalized, and ‘Halloween’ is no exception. It comes from the phrase ‘All Hallows’ Eve,’ which is the evening before All Hallows’ Day, or All Saints’ Day. Because Halloween refers to this distinct day with its own customs, traditions, and significance, it is classified as a proper noun.