Aggression-related sexual fantasies (ASF) are considered an important risk factor for sexual aggression, but empirical knowledge is limited, in part because previous research has been based on predominantly male, North-American college samples, and limited numbers of questions. The present study aimed to foster the knowledge about the frequency and correlates of ASF, while including a large sample of women and a broad range of ASF. A convenience sample of N = 664 participants from Germany including 508 (77%) women and 156 (23%) men with a median age of 25 (21-27) years answered an online questionnaire. Participants were mainly recruited via social networks (online and in person) and were mainly students. We examined the frequencies of (aggression-related) sexual fantasies and their expected factor structure (factors reflecting affective, experimental, masochistic, and aggression-related contents) via exploratory factor analysis. We investigated potential correlates (eg, psychopathic traits, attitudes towards sexual fantasies) as predictors of ASF using multiple regression analyses. Finally, we examined whether ASF would positively predict sexual aggression beyond other pertinent risk factors using multiple regression analysis. The participants rated the frequency of a broad set of 56 aggression-related and other sexual fantasies, attitudes towards sexual fantasies, the Big Five (ie, broad personality dimensions including neuroticism and extraversion), sexual aggression, and other risk factors for sexual aggression. All participants reported non-aggression-related sexual fantasies and 77% reported at least one ASF in their lives. Being male, frequent sexual fantasies, psychopathic traits, and negative attitudes towards sexual fantasies predicted more frequent ASF. ASF were the strongest predictor of sexual aggression beyond other risk factors, including general aggression, psychopathic traits, rape myth acceptance, and violent pornography consumption. ASF may be an important risk factor for sexual aggression and should be more strongly considered in prevention and intervention efforts. The strengths of the present study include using a large item pool and a large sample with a large proportion of women in order to examine ASF as a predictor of sexual aggression beyond important control variables. Its weaknesses include the reliance on cross-sectional data, that preclude causal inferences, and not continuously distinguishing between consensual and non-consensual acts. ASF are a frequent phenomenon even in in the general population and among women and show strong associations with sexual aggression. Thus, they require more attention by research on sexual aggression and its prevention.