"Diet Pepsi" is a song by American singer and songwriter Addison Rae. It was released on August 9, 2024, through Columbia Records, as her major label debut single, marking also her first single release in three years since "Obsessed" (2021). "Diet Pepsi" received positive reviews unlike the former, and charted in several countries worldwide. The pop and synth-pop song with a prominent alternative pop sound is about "the immortal feeling of being young and in love."

"Diet Pepsi" emerged as Rae's early breakthrough, peaking at number 54 on the Billboard Hot 100. Outside of the United States, "Diet Pepsi" peaked within the top ten of the charts in Ireland, Singapore, and the United Kingdom, and peaked within the top 20 of the charts in Australia, New Zealand, and the Philippines. Critics praised Rae's vocal performance and use of modulation, and compared the song favorably to the early work of Lana Del Rey. "Diet Pepsi" appeared on numerous critics' and music publications' rankings of the best songs of 2024.