Samuel Karlin was an American mathematician at Stanford University in the late 20th century. He was born on June 8, 1924 in Poland. Karlin earned his undergraduate degree from Illinois Institute of Technology; and then his doctorate in mathematics from Princeton University in 1947 under the supervision of Salomon Bochner. He was on the faculty of Caltech from 1948 to 1956, before becoming a professor of mathematics and statistics at Stanford. He was a pioneer in the application of mathematics and statistical models to problems in biological sequence analysis. He worked in this field for the last 20 years or so. He wrote many important papers in bioinformatics, but probably the most influential was a series of papers with Stephen Altschul in the early 1990s laying out the statistical foundation for BLAST, the most frequently used piece of software in computational biology. He was the author or coauthor of 10 books and more than 450 published papers, and the recipient of many awards and honors, including membership in the American Academy of Arts and Sciences and the National Academy of Sciences. He was awarded the National Medal of Science in 1989. He died on December 18, 2007 in Palo Alto, California, United States.