The Atletico Madrid defender made his senior debut for Spain in 2020 and was part of the squad that won the 2026 FIFA World Cup in July after beating Argentina 1-0 in the final. Llorente remained an unused substitute in the decisive match.
Despite still believing he had years left at international level, Llorente said he had made the decision after careful consideration.
"I realise that I'm still young and that, perhaps, if I continued to perform well, I'd still have years left to play in this jersey," Llorente wrote on Instagram.
"I know many of you won't understand this, and I probably wouldn't have understood it either if I were looking at it from the outside. But it's a personal decision - one that I've thought through very carefully and, above all, one that comes from the heart."
Llorente also paid tribute to his Spain teammates and looked back on the memorable World Cup campaign.
"I'll cherish everything I've experienced, but above all, these last 52 days," he said.
"With a wonderful group that fought until the very end to put Spain at the top. And that's exactly what they did."
The former Real Madrid player leaves international football with a World Cup winners' medal and the satisfaction of being part of a Spain squad that reached the top of world football.
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