To help boost the number of women entering physics careers, the well-established program International Masterclasses is holding special events on the UN International Day of Women and Girls in Science (February 11). Girls aged 15-19 participate in a Masterclass under the supervision of female facilitators, who serve as role models. Particle Physics Masterclasses, organized by the International Particle Physics Outreach Group (IPPOG), are a proven tool to engage high school students with particle physics. In a Masterclass, participants learn about high energy physics in a day-long course and perform a tailor-made physics analysis with real LHC data. In 2020, universities and research labs organized 17 Masterclasses for girls, with participation from three continents. About 600 girls attended the Masterclasses. videoconferences with CERN were held where the girls could talk to CERN women scientists and learn about the careers of these role models.