Bellur Krishnamachar Sundararaja Iyengar (1918–2014) was an Indian yoga guru and the founder of Iyengar Yoga, a style of yoga that emphasizes precise alignment and detailed instruction. He became one of the foremost yoga teachers in the world, with his teachings spreading globally.

Iyengar's approach to yoga involved holding poses for extended periods, focusing on the correct anatomical alignment of each posture. This method aimed to develop strength, flexibility, stability, and balance. He also developed a system of using props, such as blocks, straps, and blankets, to help students achieve correct alignment and deepen their practice, making yoga accessible to a wider range of people.

His influence on modern yoga is substantial. Iyengar authored several influential books on yoga, including "Light on Yoga," which has been translated into numerous languages and is considered a foundational text for many yoga practitioners. His legacy continues through the thousands of certified Iyengar Yoga teachers worldwide and the enduring popularity of his method.

B. K. S. Iyengar is primarily known as the founder of Iyengar Yoga, a distinct style of Hatha Yoga. His method is characterized by meticulous attention to anatomical detail and precise alignment in each asana (posture). Iyengar emphasized holding poses for extended durations to cultivate strength, stability, and flexibility. He also pioneered the use of props like blocks, blankets, and belts to assist practitioners in achieving correct alignment and to make the practice accessible to individuals of varying physical abilities and limitations. This innovative approach made yoga more systematic and therapeutic.

Iyengar's teachings gained international recognition, leading to the establishment of Iyengar Yoga institutes and certified teachers across the globe. He traveled extensively, conducting workshops and teacher training programs that disseminated his methodology. His seminal work, "Light on Yoga," published in 1966, became a comprehensive guide to yoga postures and philosophy, translated into over 30 languages and widely regarded as a definitive text. His influence extended to prominent figures, including writers and philosophers, who often credited his teachings with improving their physical and mental well-being.