The 21-year-old pulled out an astonishing late sprint to deliver a time of 4 minutes and seven-hundredths of a second, still only enough for sixth place in a high-quality field but sufficient to erase Yvonne Murray's 1987 mark from the books and to move up to fifth in the UK's all-time rankings at the distance.
"I just thought it was the perfect opportunity to run a fast race," she said. "If I'd got a personal best, I'd have been happy. That's two seconds off. Four minutes was so close. But I wasn't aiming for sub-4 at the moment so I'm delighted. Records are meant to be broken but medals will stay with you forever. My aim is for championships but to get a time like that, I'm so happy."
Muir will now revert to the 800 metres for the Sainsbury's Glasgow Grand Prix where she is slated to take on fellow Scot Lynsey Sharp on Saturday. With the European champion fresh from breaking the two-minute barrier for the first time, it promises to be a landmark battle.
"I don't know if we've ever raced before," said Muir. "I came on the scene last year when she was out injured so it's funny it's happening now on such a big stage. But that will be good. The race is going to be very competitive. And maybe the crowd won't know who to cheer for but it's great to see Lynsey right up there."
Muir's scything of over a second from the existing Scottish best earned praise from Liz Lynch who was just behind Murray when the pair duelled for supremacy in Oslo 27 years and one day earlier. "About time," the former world champion declared. And Scottish Athletics head coach Stephen Maguire believes it is now impossible to under-state the prospective accomplishments.
"Laura runs with an openness and fluidity and who knows what's possible now?" he said. "She's fifth in the UK all-time list and she's got the Scottish record. Rivals around the world certainly know who Laura Muir is."
Elsewhere in Paris, Eilish McColgan confessed to a lack of race fitness after fading during the closing stages of the 3000m steeplechase to end up in 13th.
Alysson Felix, also Glasgow-bound this week, showed she is almost recovered from a hamstring problem by coming second to Blessing Okagbare in the 200m while Asbel Kiprop, gearing up for a tilt at the world 1500m record in Monaco in two weeks time, produced the fastest 800m this year of 1:43.34 in a high-quality field.