Muir’s continental win adds to Olympic silver, world bronze and Commonwealth gold over the past 12 months.
Mageean, who also took second in Muir’s wake at Birmingham 2022, finished in a season’s best four minutes 02.56 seconds, just less than a second and a half off the winner.
Muir’s team-mate Katie Snowden took fourth, with compatriot Ellie Baker in eighth. Poland’s Sofia Ennaoui, who finished fifth at the recent World Championships, took bronze after being caught out of position when Muir and Mageean kicked for home.
The third and final peak in a log-jammed summer of championships proved the toughest to climb admitted Muir afterwards.
“This summer looked hard on paper but doing it in person? Never again,” she told BBC Sport.
“This was the hardest one. It looked the easiest with only one event and two rounds, but it was so tough mentally, it was the most difficult race I have ever run, honestly.”
Just as in her win in Berlin four years ago, the Netherlands’ Sifan Hassan was missing from the field, which made Muir’s task easier.
But there is little doubt that Muir is now a better athlete – both in numbers and neckwear.
Six of her seven fastest times over 1500m have come since her last European title, while a sudden glut of major medals, after a series of big-event disappointments, have confirmed her as a contender in any company.
Muir’s confidence was clear as she lurked at the back of the pack on the opening lap, before moving up, taking control and blowing the field apart.
As Muir rounded for home and gritted her teeth with Mageean still in striking distance, it briefly looked as if she may have misjudged her move.
But her reserves of stamina and determination proved more than deep enough to bail her out as she won in some comfort.
The Scot flopped to the track over the line and lay hand in hand with Mageean as both recovered from another draining duel.
