Ciara Mageean clocked a season's best of four minutes 2.48 seconds to finish in fifth place behind Kenya's Faith Kipyegon in the 1500m in Monaco on Friday.
Mageean had only ever covered the distance faster on three previous occasions, with the time bettering her previous season best of 4:04.32 that she set at the Florence Diamond League.
The time also means the 29-year-old has achieved automatic qualification for the 2022 World Championships in Oregon.
The prestigious Diamond League meeting marked Mageean's final race before the Tokyo Games, with the Portaferry star eyeing a place in a first Olympic final.
Pacemaker Chanelle Price ensured a fast early tempo, with defending Olympic champion Kipyegon finishing a second outside the world record in 3:51.07, which is the fastest time run in the world this year and the fourth fastest time in history.
Sifan Hassan of the Netherlands led narrowly as the bell sounded for the final lap, but she had no answer to the devastating kick of the Kenyan as they rounded the final bend into the home straight.
Hassan's final time was still good enough to produce a season's best, while 20-year-old Freweyni Hailu of Ethiopia clocked a personal best in third.
Elsewhere, David Kenny won Ireland's first ever race walk medal at the European Under-23 Championships in Tallinn, producing an excellent performance to take silver in Estonia.
The Olympic-bound Kerryman finished the 20km walk in 1:25.50 behind Spaniard José Manuel Perez, who clocked 1:25:06.
Kenny, trained by Rob Heffernan, sat comfortably on the shoulder of the leader in second place at the 10km mark and paced himself well to claim the historic silver.
It's Ireland’s ninth medal at the championships since they began in 1997.
