Pafnuty Lvovich Chebyshev is a mathematician perhaps best known for contributing one of the founding theorems to the area of probability theory. His famed theory, known as Chebyshev's inequality, helped to establish a mathematical basis for the likelihood of a random variable taking a value far from its expected value.

Chebyshev was born into the gentry in Okatovo, Russia in 1821. His father was a retired army officer who fought in the wars against Napoleon. In 1832, the family moved to Moscow so that the nine Chebyshev children could have the opportunity for a better education. Pafnuty took advantage of the opportunity, completing his high school education in Moscow and entering the Department of Physics and Mathematics at Moscow University in the late 1830s.

As a student, Pafnuty gained the notice of the academic community in Moscow by developing a method for approximating the roots of equations. Young Pafnuty graduated from the university in 1841 with a degree in mathematics, but he continued to study mathematics in Moscow, completing his master's exam in 1843 and finishing his thesis in 1846.

Chebyshev was appointed in 1847 to a position as an assistant at the University of St. Petersburg, where he wrote and defended a thesis in the late 1840s. In 1860 he was made a full professor there, and continued to serve there until his retirement due to poor health in 1882. Chebyshev passed away in 1894.

Besides his famous inequality, Chebyshev contributed quite a lot to numerous mathematical and physical fields. He wrote a book on the theory of congruences in 1849 that would become a strongly influential work in the later development of number theory. His work on the distribution of prime numbers was lauded in the mathematical community, as was his proof of Bertrand's conjecture which stated for every integer n > 3, there is a prime number between n and 2n - 2. He also was responsible for some of the foundational work in the proof of the prime number theorem. He also provided some valuable work in the approximation of functions using polynomials which is still used today in the field of computer science for quick polynomial approximation. Chebyshev also dabbled in mechanics, studying the conversion of rotary motion into rectilinear motion by mechanical coupling; the Chebyshev parallel motion is three linked bars that approximate rectilinear motion.

Pafnuty Chebyshev was one of many men who helped to found modern mathematics. Many of the principles he discovered are still in use today in mathematics, computer science, and mechanics.