The midfielder has arrived from Strasbourg for a club record fee of £30m.
“We’re very happy,” said Le Bris. “We chose each other, but most of all Habib chose Sunderland.
“It’s normal for a profile like him to have interest from top clubs across Europe, and the fact he picked us shows he shares our ambition and vision. He immediately connected with the values of the club - strong team spirit, high energy, and leadership.
“He can give a huge contribution to the group, because he brings qualities that align perfectly with what we’re building, both on and off the pitch, as we take this next step into the Premier League.”
Perfect for Premier League
At 21, Senegal international Diarra captained Strasbourg last season.
Le Bris added: “Age is only a number when you have his personal and technical qualities.
“Playing in that demanding position on the international stage, Habib proved he belongs to this level, Premier League perfectly fits to his profile.
“This next step - performing in a top league - is a big challenge, but it matches his ambition and his desire to keep progressing.”