Nafissatou "Nafi" Thiam is a Belgian athlete specialising in multi-event competition. She is a two-time Olympic gold medalist, winning the heptathlon event at the 2016 Rio and 2020 Tokyo Olympics. Thiam is the only Belgian athlete, male or female, to successfully defend an Olympic title and only the second woman after Jackie Joyner-Kersee to win back-to-back Olympic titles in the event.

A heptathlon is a track and field combined events contest made up of seven events. The name derives from the Greek επτά and ἄθλος. A competitor in a heptathlon is referred to as a heptathlete.