Sunderland sign N'Diaye from Bursaspor
The 22-year-old midfielder completed a medical at the Stadium of Light and has signed a three-and-a-half-year contract to the delight of manager Martin O'Neill.
"Alfred is a strong, powerful young player and as such can offer us more strength in depth," he told Sunderland's website.
"He will give us options and I'm delighted that we have been able to bring him to the club."
The France under-21 international, who began his career with Nancy, is Sunderland's first signing in the January transfer window.