The main functions of a saddle are to improve rider stability and comfort, with the stirrups providing support for the rider’s legs. The criteria upon which riders base their choice of stirrup length for different equestrian disciplines does not appear to have been reported. Therefore, this study was designed to investigate the factors that play a role in a rider’s choice of stirrup length for different equestrian and para-equestrian disciplines. An online questionnaire consisting of open and closed demographic questions, and 28 Likert scale questions related to factors which are anecdotally associated with stirrup length was distributed via social media horse pages. Respondents were asked to identify factors that influenced their decision making when setting their stirrup length in dressage, showjumping and eventing (dressage, showjumping and cross-country phases). 2,183 participants took part in this study, the majority were female (97%; n=2,131). 8% of the sample (n=184) categorised themselves as para-equestrians. Most respondents (n=1,200) identified themselves as dressage riders (amateur: 89%, n=1,068; professional: 11%, n=132), 665 riders engaged in showjumping (amateur: 87%, n=579; professional: 13%, n=86) and a further 393 riders selected eventing as their primary discipline (amateur: 89%, n= 350; professional: 11%, n=43). All riders consistently ranked feel of stirrups once mounted, how stable stirrups feel once moving and type of saddle being used as the three most important factors when deciding stirrup length across the disciplines. Dressage riders were more greatly influenced by the factors investigated when setting stirrup length then either showjumping or event riders (Kruskal Wallis: P<0.04). For eventing participants, exercise type, safety, saddle type and rider stability were key factors influencing stirrup length selection between different phases of the competition. These factors were generally ranked as more important for the dressage/flatwork phase compared to showjumping or cross country schooling (Kruskal Wallis: P<0.01). Stirrup length is likely to affect rider comfort, performance and safety while having relatively less effect on the horse’s well-being, therefore it is not surprising that riders from all disciplines placed high emphasis on factors related to the rider and saddle.