Perez's future has been the subject of endless speculation due to the large performance gap between him and team-mate Max Verstappen this year, with the Dutchman romping to his ninth consecutive victory at Sunday's Dutch Grand Prix.
Recent comments by Red Bull advisor Helmut Marko further added fuel to the fire, the Austrian suggesting in several German-language interviews Perez was not 100% certain to take up his seat in 2024 despite a running contract.
Daniel Ricciardo's return with AlphaTauri is widely seen as an audition for Perez' Red Bull seat, albeit more for 2025 rather than next year.
Speaking after the Zandvoort race, Horner has formally confirmed in no uncertain terms that Perez will retain his seat in 2024, despite Marko's comments.
"Checo's situation for next year is clear," Horner stated. "He's a Red Bull Racing driver. We have an agreement with him.
"Irrelevant of agreements, we're pleased with the job that he's doing. You saw his drive today, he was unlucky with the pit lane speed limiter [which cost Perez a five-second penalty that dropped him off the podium to fourth].
"He's second in the world championship, he's the only driver rather than Max to have won grands prix this year.
"It's easy to beat up on him when the barometer is so high on the other side, but he will be our driver in 2024."
Horner pointed out Verstappen was not just dominating his team-mate, but also the rest of the grid as he scythed up the order during the early, wet laps of the Dutch Grand Prix after coming in a lap too late for intermediates and ceding the lead to Perez.
"Max is in a period of his career where he's just simply untouchable and I don't think there's any driver on the grid that would be able to achieve what he's been doing in that car," he added.
"Being his team-mate is probably in some respects the most unenviable job to have because the barometer is so high.
"You've got to look at the performance on the timesheet and the results sheet. If Max hadn't been there, Checo would have won another four or five races.
"So, he's doing his job. He's second in the world championship. You saw his performance today. He was unlucky to get the speeding fine. And hopefully he can add to his wins before the end of the year."
Additional reporting by Erwin Jaeggi
