Bellur Krishnamachar Sundararaja Iyengar (14 December 1918 – 20 August 2014) was an Indian teacher of yoga and author.

[12] Iyengar's home town, Bellur, was in the grip of the influenza pandemic at the time of his birth, and an attack of that disease left the young boy sickly and weak for many years.

"[13] In 1934, B. K. S. Iyengar's brother-in-law, the yogi Sri Tirumalai Krishnamacharya, asked him to come to Mysore, so as to improve his health through the practice of yoga asanas.

[12][18] Though Iyengar had very high regard for Krishnamacharya,[16] and occasionally turned to him for advice, he had a troubled relationship with his guru during his tutelage.

[22] Menuhin gave him the opportunity that transformed Iyengar from a comparatively obscure Indian yoga teacher into an international guru.

Because Iyengar had taught the famous philosopher Jiddu Krishnamurti, he was asked to go to Bombay to meet Menuhin, who was known to be interested in yoga.

[26] Among his other devotees were the novelist Aldous Huxley, the actress Annette Bening, the film maker Mira Nair and the designer Donna Karan, as well as prominent Indian figures, including the cricketer Sachin Tendulkar and the Bollywood actress Kareena Kapoor.

[19] He conducted demonstrations and later, when a scooter accident dislocated his spine, began exploring the use of props to help disabled people practice Yoga.

He drew inspiration from Hindu deities such as Yoga Narasimha and stories of yogis using trees to support their asanas.

[32] In Goldberg's view, Iyengar "rationalized his humiliation of his followers as a necessary consequence of his demand for high standards",[33] but this was consistent with his childhood response to the rough and abusive treatment he received from Krishnamacharya, taking offence quickly, being suspicious of other people's intentions, and belittling others: "In other words, he sometimes behaved like Krishnamacharya".

[33] Goldberg concludes, however, that Iyengar hid "a compassion of which Krishnamacharya was never capable", and his students remembered his playfulness as well as his unpredictable temper.

2 million to Chamarajendra Zoological Gardens, Mysore, thought to be the largest donation by an individual to any zoo in India.

[35] Iyengar's most important charitable project involved donations to his ancestral village of Bellur, in the Kolar district of Karnataka.

Through the Bellur Trust fund which he established, he led a transformation of the village, supporting a number of charitable activities there.

Since Geeta's death, Prashant has served as the director of the Ramamani Iyengar Memorial Yoga Institute (RIMYI) in Pune.

[3] Anthropologist Joseph S. Alter of the University of Pittsburgh stated that Iyengar "has by far had the most profound impact on the global spread of yoga.

[42] The noun "Iyengar", short for "Iyengar Yoga", is defined by Oxford Dictionaries as "a type of Hatha yoga focusing on the correct alignment of the body, making use of straps, wooden blocks, and other objects as aids in achieving the correct postures.

[45] Leap of Faith (2008), another documentary film by Aditi Makim and Valentina Trivedi, covered his life from childhood to adulthood and the hurdles he faced in his career.