Satyendra Nath Bose (1 January 1894 – 4 February 1974), FRS, was an Indian physicist, specializing in mathematical physics. He is best known for his work on quantum mechanics in the early 1920s, providing the foundation for Bose-Einstein statistics and the theory of the Bose-Einstein condensate. He is honoured as the namesake of the boson. He was awarded India's second highest civilian award, the Padma Vibhushan in 1954 by the Government of India.

Although more than one Nobel Prize was awarded for research related to the concepts of the boson, Bose-Einstein statistics and Bose-Einstein condensate — the latest being the 2001 Nobel Prize in Physics, which was given for advancing the theory of Bose-Einstein condensates — Bose himself was not awarded the Nobel Prize. Among his other talents, Bose spoke several languages and could also play the esraj, a musical instrument similar to a violin. In his book, The Scientific Edge, the noted physicist Jayant Narlikar observed:

Bose was born in Kolkata (Calcutta), India, the eldest of seven children. His father, Surendranath Bose, worked in the Engineering Department of the East Indian Railway Company. Bose attended Hindu School in Calcutta, and later attended Presidency College, also in Calcutta, earning the highest marks at each institution. He came in contact with teachers such as Jagadish Chandra Bose and Prafulla Chandra Roy who provided inspiration to aim high in life. From 1916 to 1921 he was a lecturer in the physics department of the University of Calcutta. In 1921, he joined the department of Physics of the then recently founded Dhaka University (now in Bangladesh and called University of Dhaka).

In 1924, while working as a Reader at the Physics Department of the University of Dhaka, Bose wrote a paper deriving Planck's quantum radiation law without any reference to classical physics and using a novel way of counting states with identical particles. This paper was seminal in creating the very important field of quantum statistics. After initial setbacks to his efforts to publish, he sent the article directly to Albert Einstein in Germany. Einstein, recognizing the importance of the paper, translated it into German himself and submitted it on Bose's behalf to the prestigious Zeitschrift für Physik. As a result of this recognition, Bose was able to leave India for the first time and spent two years in Europe, during which he worked with Louis de Broglie, Marie Curie, and Einstein.

After his European sojourn Bose returned to Dhaka in 1926. He became a professor and was made head of the Department of Physics, and continued teaching at Dhaka University until 1945. He was also Dean of the Faculty of Science at Dhaka University for a long period. When the partition of India became imminent, he returned to Calcutta and taught at Calcutta University until 1956, when he retired and was made professor emeritus.

While presenting a lecture at the University of Dhaka on the theory of radiation and the ultraviolet catastrophe, Bose intended to show his students that the contemporary theory was inadequate, because it predicted results not in accordance with experimental results. During this lecture, Bose committed an error in applying the theory, which unexpectedly gave a prediction that agreed with the experiment. (He later adapted this lecture into a short article called Planck's Law and the Hypothesis of Light Quanta.) The error was a simple mistake — similar to arguing that flipping two fair coins will produce two heads one-third of the time — that would appear obviously wrong to anyone with a basic understanding of statistics. However, the results it predicted agreed with experiment, and Bose realized it might not be a mistake at all. He for the first time took the position that the Maxwell-Boltzmann distribution would not be true for microscopic particles where fluctuations due to Heisenberg's uncertainty principle will be significant. Thus he stressed the probability of finding particles in the phase space, each state having volume h³, and discarding the distinct position and momentum of the particles.

Physics journals refused to publish Bose's paper. It was their contention that he had presented to them a simple mistake, and Bose's findings were ignored. Discouraged, he wrote to Albert Einstein, who immediately agreed with him. His theory finally achieved respect when Einstein sent his own paper in support of Bose's to Zeitschrift für Physik, asking that they be published together. This was done in 1924. Bose had earlier translated Einstein's theory of General Relativity from German to English. The reason Bose's "mistake" produced accurate results was that since photons are indistinguishable from each other, one cannot treat any two photons having equal energy as being two distinct identifiable photons. By analogy, if in an alternate universe coins were to behave like photons and other bosons, the probability of producing two heads would indeed be one-third (tail-head = head-tail). Bose's "error" is now called Bose-Einstein statistics.

Einstein adopted the idea and extended it to atoms. This led to the prediction of the existence of phenomena which became known as Bose-Einstein condensate, a dense collection of bosons (which are particles with integer spin, named after Bose), which was demonstrated to exist by experiment in 1995.

Bose's ideas were afterwards well received in the world of physics, and he was granted leave from the University of Dhaka to travel to Europe in 1924. He spent a year in France and worked with Marie Curie, and met several other well-known scientists. He then spent another year abroad, working with Einstein in Berlin. Upon his return to Dhaka, he was made a professor in 1926. He did not have a doctorate, and so ordinarily he would not be qualified for the post, but Einstein recommended him. His work ranged from X-ray crystallography to unified field theories. He also published an equation of state for real gases with Megh Nad Saha.

Apart from physics he did some research in biochemistry and literature (Bengali, English). He made deep studies in chemistry, geology, zoology, anthropology, engineering and other sciences. Being an Indian of Bengali descent, he devoted a lot of time to promoting Bengali as a teaching language, translating scientific papers into it, and promoting the development of the region.

In 1944 Bose was elected General President of the Indian Science Congress. In 1958 he became a Fellow of the Royal Society.