The current Loughborough University student (Geography and Sport Science) produced a stunning performance in the Women’s 50m Backstroke to make the podium.
The 21-year-old timed her swim to perfection, keeping established international talent away to hit the wall in a time of 27.20.
Cox’s swim secured GB’s first medal of the meet and the first individual women's medal at a World Champs for Britain since 2015.
Speaking to British Swimming, she said: “I'm over the moon, it's such a good feeling, it's amazing. I couldn't believe it, to be honest! I needed to look for about 30 seconds at the board before I could be like, 'wow, that's me!'" said Cox.
“I couldn't have asked for any more here. When I got here, my goal was to make a final, so to come away with a medal is just incredible. My 100m has gone well, but there's stuff to work on which is super motivating. I'm more motivated than ever to get back for next season and see what I can do at trials in April for Paris.”
Elsewhere, there was bittersweet success for Loughborough and Northern Ireland star Daniel Wiffen.
The Commonwealth Games silver medallist broke yet another European Record after finishing fourth in the Men’s 800m freestyle and agonisingly missed out on a medal by also finishing fourth in the Men’s 1500m freestyle.
Speaking to BBC Sport, he said: "There is bitter disappointment at going into the final with the fastest time and finishing fourth but that's sport I guess, I'll just have to go away and train harder and get faster.
"I had an idea about how the race was going to work out but on the day, I just wasn't good enough to keep up with the pace. I wanted to win that race and I didn't, I came fourth. I'll go home, I have the European under-23s in Dublin to look forward to and I'm going to focus on that, and I want to post some fast times there and then next season just go for that gold in Paris.”
Wiffen’s performances helped Ireland achieve its best-ever set of results at a World Championships.