Although gender parity has been reached at the graduate level in the geosciences, women remain a minority in faculty positions. First authorship of peer‐reviewed scholarship is a measure of academic success and is often used to project potential in the hiring process. Given the importance of first author publications for hiring and advancement, we sought to quantify whether women are underrepresented as first authors relative to their representation in the field of geoscience. We compiled first author names across 13 leading geoscience journals from January 2013 to April 2019 (n 1⁄4 35,183). Using a database of 216,286 names from 79 countries, across 89 languages, we classified the likely gender associated with each author's given (first) name. We also estimated the gender distribution of authors who publish using only initials, which may itself be a strategy employed by some women to preempt perceived (and actual) gender bias in the publication process. Female names represent 13–30% of all first authors in our database and are substantially underrepresented relative to the proportion of women in early career positions (30–50%). The proportion of female‐name first authors varies substantially by subfield, reflecting variation in representation of women across geoscience subdisciplines. In geoscience, the quantification of this first authorship gender gap supports the hypothesis that the publication process—namely, achievement or allocation of first authorship—is biased by social factors, which may modulate career success of women in the sciences.