The history and evolution of Gaussian basis sets in molecular electronic structure calculations are reviewed, from the original proposals by McWeeny and Boys to the current high‐quality generally‐contracted basis sets of the atomic natural orbital and correlation‐consistent types. Various explorations of modified forms, generalizations, and alternatives are mentioned, but the focus is on the mainstream developments whose origin can largely be traced to the work of Reeves and his students. The introduction of various standard sequences of basis sets, such as those of Pople and coworkers, with well‐documented and extensive test results, and the wide distribution of easy‐to‐use computer codes, such as the GAUSSIAN series, have contributed greatly to the explosion in the use of ab initio calculations of molecular structure in the chemistry research community.