Bencic was born in Switzerland to Slovak parents; she began playing tennis at the age of two. Her father arranged for her to train with Martina Hingis’s mother and coach Melanie Molitor daily from the age of seven.
By the time she was 16, Bencic was the No. 1 ranked junior in the world and won two junior Grand Slam singles titles at the French Open and Wimbledon. On the professional tour, she made her top 100 debut shortly after turning 17. Her big breakthrough came at the 2014 US Open, where she became the youngest quarterfinalist since Hingis in 1997. Bencic won her first two WTA Tour titles in 2015, including the Canadian Open where she defeated four of the top six players in the world. She then made her top-ten debut the following year while still 18 years old.
From 2016 through 2018, Bencic struggled with a variety of injury issues, most notably needing to have wrist surgery in 2017 that kept her out for five months and saw her drop outside the top 300 in the WTA Rankings.