Kayla Itsines is an Australian personal trainer, entrepreneur, and author known for her fitness programs and workout guides. She gained popularity through her Bikini Body Guide (BBG) series, which focuses on high-intensity interval training (HIIT) and strength training. Her approach emphasizes short, effective workouts that can be done at home or in the gym. In addition to her fitness programs, Kayla Itsines co-founded the Sweat app, which offers a variety of workout plans and nutrition advice. She has built a large online community, inspiring millions of women worldwide to lead healthier lifestyles through exercise and proper nutrition.