UFC on Fox 23: Shevchenko vs. Peña: UFC on Fox 23: Shevchenko vs. Peña was a mixed martial arts event promoted by the Ultimate Fighting Championship held on January 28, 2017 at Pepsi Center in Denver, Colorado. A potential UFC Women's Bantamweight Championship title eliminator between multiple-time muay thai world champion Valentina Shevchenko and The Ultimate Fighter: Team Rousey vs. Team Tate bantamweight winner Julianna Peña served as the event headliner.