Background: Gender disparities in authorship of heart failure (HF) guideline citations and clinical trials have not been examined. Methods: We identified authors of publications referenced in Class I Recommendations in United States (n=173) and European (n=100) HF guidelines and of publications of all HF trials with >400 participants (n=118) published between 2001 and 2016. Authors’ genders were determined, and changes in authorship patterns over time were evaluated with linear regression and nonparametric testing. Results: The median proportion of women authors per publication was 20% (interquartile range [IQR], 8%–33%) in United States guidelines, 14% (IQR, 2%–20%) in European guidelines, and 11% (IQR, 4%–20%) in HF trials. The proportion of women authors increased modestly over time in United States and European guidelines’ references (β=0.005 and 0.003, respectively, from 1986 to 2016; P <0.001) but not in HF trials (12.5% [IQR, 0%–20%] in 2001–2004 to 8.9% [IQR, 0%–20%] in 2013–2016; P >0.50). Overall proportions of women as first or last authors in HF trials (16%) did not change significantly over time ( P =0.60). North American HF trials had the highest likelihood of having a woman as first or senior author (24%). HF trials with a woman first or senior author were associated with a higher proportion of enrolled female participants (39% versus 26%, P =0.01). Conclusions: In HF practice guidelines and trials, few women are authors of pivotal publications. Higher number of women authors is associated with higher enrollment of women in HF trials. Barriers to authorship and representation of women in HF guidelines and HF trial leadership need to be addressed.