What is biggest hit song?

According to Billboard, the biggest hit song of all time is "Blinding Lights" by The Weeknd. The song was released in November 2019 and spent a record-breaking 90 weeks on the Billboard Hot 100 chart, including four weeks at number one. The song also reached the top of the charts in many other countries around the world and has been certified multi-platinum by the Recording Industry Association of America (RIAA).