Defender Fonte has helped Saints climb from League One to the Europa League during his six-year stint on the south coast.
His performances for Southampton finally drew him to the attention of Portugal boss Fernando Santos who handed Fonte his senior international debut 17 months ago.
Fonte has since played nine times for his country and is desperate to star at the Euros this summer.
He said: “Everyone wants to be at the Euros, and I’m no exception to that.
“I want to give my best, I’ve tried to give my best when I’ve been called up and now it remains for me to work at my club, keep healthy, without injuries and hope I impress the national team coach.”