Abstract: Disclosed herein are dilators for vascular access systems, and associated devices and methods. In some embodiments, a dilator includes an elongate body having a diameter that is generally constant or uniform along the length of the body. The diameter can be sized to correspond with a catheter of a vascular access system, such that the dilator can be positioned within the catheter with little or no gaps or spacing between the dilator and an interior of the catheter. Additionally, or alternatively, the body of the dilator can include multiple body regions, each having one or more respective mechanical properties. In these and other embodiments, the dilator can be configured to interface with at least a portion of the vascular access system. For example, the dilator can include one or more notches configured to couple the dilator to the vascular access system via a valve of the vascular access system.