...Baby One More Time — Britney Spears (1998)

Max Martin's production—a hypnotic mix of shuffling percussion and a descending synth hook—turned a school-corridor fantasy into a global anthem. The song's music video, featuring Britney's iconic schoolgirl outfit, became a defining visual of the decade, setting a benchmark for pop star image-making that remains unequaled. It topped the Billboard Hot 100 for two weeks and launched Spears as the best-selling teen artist of the era, eventually moving over 10 million units worldwide.