Alfred Charles Kinsey (/ˈkɪnzi/; June 23, 1894 – August 25, 1956) was an American sexologist, biologist, and professor of entomology and zoology who, in 1947, founded the Institute for Sex Research at Indiana University, now known as the Kinsey Institute for Research in Sex, Gender, and Reproduction. He is best known for writing Sexual Behavior in the Human Male (1948) and Sexual Behavior in the Human Female (1953), also known as the Kinsey Reports, as well as for the Kinsey scale. Kinsey's research on human sexuality, foundational to the field of sexology, provoked controversy in the 1940s and 1950s, and has continued to provoke controversy decades after his death. His work has influenced social and cultural values in the United States and United Kingdom as well as internationally.

Alfred Kinsey was born on June 23, 1894, in Hoboken, New Jersey, the son of Sarah Ann (née Charles) and Alfred Seguine Kinsey. He was the eldest of three children. His mother received little formal education; his father was a professor at Stevens Institute of Technology.

Kinsey's parents were devout Christians. His father was known as one of the most devout members of the local Methodist church. Most of Kinsey's social interactions were with other members of the church, often as a silent observer, while his parents discussed religion. Kinsey's father imposed strict rules on the household, including mandating Sunday as a day of prayer and little else.

Kinsey's parents were poor for most of his childhood, often unable to afford proper medical care. This may have led to a young Kinsey receiving inadequate treatment for a variety of diseases including rickets, rheumatic fever, and typhoid fever. His health records indicate that Kinsey received suboptimal exposure to sunlight (often the cause of rickets, before milk and other foods were fortified with vitamin D) and lived in unsanitary conditions for at least part of his childhood. Rickets led to a curvature of the spine, which resulted in a slight stoop that prevented Kinsey from being drafted in 1917 for World War I.

At age 10, Kinsey moved with his family to South Orange, New Jersey. Also at a young age, he showed great interest in nature and camping. He worked and camped with the local YMCA throughout his early years, and enjoyed these activities to such an extent that he intended to work for the YMCA after completing his education. Kinsey's senior undergraduate thesis for psychology, a dissertation on the group dynamics of young boys, echoed this interest. He joined the Boy Scouts when a troop was formed in his community. His parents strongly supported this (and joined as well) because the Boy Scouts was an organization that was based on the principles of Christianity. Kinsey worked his way up through the Scouting ranks to earn Eagle Scout in 1913, making him one of the earliest Eagle Scouts. Despite earlier disease having weakened his heart, Kinsey followed an intense sequence of difficult hikes and camping expeditions throughout his early life.

In high school, Kinsey was a quiet but hard-working student. While attending Columbia High School, he devoted his energy to academic work and playing the piano. At one time, Kinsey had hoped to become a concert pianist, but decided to concentrate on his scientific pursuits instead. Kinsey's ability to spend immense amounts of time deeply focused on study was a trait that would serve him well in college and during his professional career. He seems not to have formed strong social relationships during high school, but earned respect for his academic ability. While there, Kinsey became interested in biology, botany and zoology. Kinsey was later to claim that his high school biology teacher, Natalie Roeth, was the most important influence on his decision to become a scientist.

Kinsey approached his father with plans to study botany at college. His father demanded that he study engineering at Stevens Institute of Technology instead. At Stevens, he primarily took courses related to English and engineering, but was unable to satisfy his interest in biology. Kinsey was not successful there, and decided engineering was not a field at which he could excel. At the end of two years at Stevens, Kinsey gathered the courage to confront his father about his interest in biology and his intent to continue studying at Bowdoin College in Brunswick, Maine, where he majored in biology.

In the fall of 1914, Kinsey entered Bowdoin College, where he studied entomology under Manton Copeland, and was admitted to the Zeta Psi fraternity, in whose house he lived for much of his time at college. In 1916 Kinsey was elected to the Phi Beta Kappa society and graduated magna cum laude, with degrees in biology and psychology. Alfred Seguine Kinsey did not attend his son's graduation ceremony at Bowdoin, possibly as another sign of disapproval of his son's choice of career and studies.