In June 2015, 15-year-old Steenbergen competed at the inaugural 2015 European Games in Baku, she won gold in 100 m freestyle ahead of Russia's Arina Openysheva clocking in at 53.97 s. Steenbergen also won five silver medals (in the 50 m freestyle, 200 m freestyle, 4 × 200 m freestyle, 4 × 100 m medley, and 4 × 100 m freestyle). The swimming part of the Games were open to junior only.