Jean Bartik (née Betty Jean Jennings; December 27, 1924 – March 23, 2011) was an American computer programmer who was one of the original six programmers of the ENIAC computer.

Bartik studied mathematics in school then began work at the University of Pennsylvania, first manually calculating ballistics trajectories and then using ENIAC to do so. The other five ENIAC programmers were Betty Holberton, Ruth Teitelbaum, Kathleen Antonelli, Marlyn Meltzer, and Frances Spence. Bartik and her colleagues developed and codified many of the fundamentals of programming while working on the ENIAC, since it was the first computer of its kind.

After her work on ENIAC, Bartik went on to work on BINAC and UNIVAC, and spent time at a variety of technical companies as a writer, manager, engineer and programmer. She spent her later years as a real estate agent and died in 2011 from congestive heart failure complications.

Content-management framework Drupal's default theme, Bartik, is named in her honor.

Born Betty Jean Jennings in Gentry County, Missouri in 1924, she was the sixth of seven children. Her father, William Smith Jennings (1893–1971) was from Alanthus Grove, where he was a schoolteacher as well as a farmer. Her mother, Lula May Spainhower (1887–1988) was from Alanthus. Jennings had three older brothers, William (January 10, 1915) Robert (March 15, 1918); and Raymond (January 23, 1922); two older sisters, Emma (August 11, 1916) and Lulu (August 22, 1919), and one younger sister, Mable (December 15, 1928).

In her childhood, she would ride on horseback to visit her grandmother, who bought the young girl a newspaper to read every day and became a role model for the rest of her life. She began her education at a local one-room school, and gained local attention for her softball skill. In order to attend high school, she lived with her older sister in the neighboring town, where the school was located, and then began to drive every day despite being only 14. She graduated from Stanberry High School in 1941, aged 16. She was given the title of salutatorian on her graduation.

She attended Northwest Missouri State Teachers College now known Northwest Missouri State University, majoring in mathematics with a minor in English and graduated in 1945. Jennings was awarded the only mathematics degree in her class. Although she had originally intended to study journalism, she decided to change to mathematics because she had a bad relationship with her adviser. Later in her life, she earned a master's degree in English at the University of Pennsylvania in 1967 and was awarded an honorary doctorate degree from Northwest Missouri State University in 2002.

In 1945, the United States Army was recruiting mathematicians from universities to aid in the war effort; despite a warning by her adviser that she would be "a cog in a wheel" with the Army, and encouragement to become a mathematics teacher instead, Bartik decided to become a human computer. Bartik's calculus professor encouraged her to take the job at University of Pennsylvania because they had a differential analyzer.