Ireland finished fourth in the 4x400m women's relay final.
Sophie Becker, Rhasidat Adeleke, Phil Healy and Sharlene Mawdsley ran a time of 3.19.90, a new national record.
USA won gold, followed by the Netherlands and Great Britain finished third.
Adeleke ran a time of 49 seconds, Mawdsley under 50 seconds and Becker, Healy under 51 seconds.
It was another heartbreaking night for Adeleke after finishing fourth just after the 400 metre final on Friday night.
After a great start from Becker, Adeleke closed the gap on the USA in a exceptional second split.
Healy kept Ireland in the hunt for medals in the third as she passed it to Mawdsley.
She ran a great time of 49.1, but was just beaten to bronze by the Netherlands.
Speaking afterwards an emotional Becker said: “We’re absolutely devastated. In a few days’ time it’s not going to hurt as much. Yeah, we’re world-class. We knew if we ran a national record we’d be in the mix for it but 3:19! I don’t think any of us believed we’d run 3:19, that’s absolutely phenomenal.
"Someone had to be fourth. It was us today, but it won’t be us next time.”
Speaking on RTÉ, Adeleke said: “I’m proud of the team, we are breaking so many barriers. It’s only onwards and upwards from here. We put our best selves on the track.”
Healy said: “To come fourth in an Olympic Games is madness. The support was unbelievable. To come away with fourth is very special,” she says teary-eyed.
Mawdsley: “When you’re out in that last leg, you do feel it’s your fault. I’m pretty devastated, I just wish I could have done it for the girls. It’s heartbreaking. I did my best, I’m devastated I couldn’t hold on, the future of sprinting is so bright.”
