Football great Frank Gifford died suddenly Sunday morning ... according to a statement from his wife Kathie Lee and their kids.
Gifford's family says he passed away of natural causes at their Connecticut home. He was 84.
Gifford was an NFL Hall of Famer with the NY Giants ... and also a famous broadcaster for "Monday Night Football" from 1971-1997.
He married Kathie Lee in 1986 and they had 2 children -- Cody and Cassidy ... who is now an actress, and had her first starring role this summer in "The Gallows."
Frank had 3 other children (and 5 grandkids) from his first marriage.