The phrase "winner announcement" means the act of officially declaring or revealing the person or group that has won a competition or contest. Full definition
I've enjoyed every minute of it and the ride ain't over yet, with Charli's announcement of her TUFF contest next week and the «Best of Show» overall winner announcement on January 2nd! (sherrimatthewsblog.com)
Trend Survivor X Storm in a D cup — Swimwear $ 200 Gift Card Giveaway winner announcement time! (trendsurvivor.com)
Shortlist selections are announced in October and Carnegie Medal winner announcements take place during the ALA Midwinter Meeting. (ala.org)