Billboard Hot 100 Number Ones: 1990 Quiz

Every distinct song that appeared at No. 1 on a Billboard Hot 100 issue dated in 1990: 26 songs across 26 chart runs and the full calendar year. The issue-date scope includes a prior-year leader that remained at No. 1 during 1990. Name the complete roster, recognize the leader for a spread of changeover dates, match songs to artists, order a selection by its first 1990 date at the top, or separate the number ones from same-year Top 10 near-misses. No year-end ranking is implied.