The 22-year-old has been linked with Everton and Real Madrid in recent weeks.
Moutinho’s contract holds a £31million release clause, according to reports.
“Joao is essential to our project. He is captain and we are not interested in the sale,” the club’s president Jose Eduardo Bettencourt told Portuguese media.
“Rumours are expected at this time, but Sporting have a very made a very clear decision – Moutinho is indispensable.”
